<?php
/**
 * To validate an email address according to RFCs 5321, 5322 and others
 *
 * Copyright © 2008-2016, Dominic Sayers					<br>
 * Test schema documentation Copyright © 2011, Daniel Marschall			<br>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *     - Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     - Redistributions in binary form must reproduce the above copyright notice,
 *       this list of conditions and the following disclaimer in the documentation
 *       and/or other materials provided with the distribution.
 *     - Neither the name of Dominic Sayers nor the names of its contributors may be
 *       used to endorse or promote products derived from this software without
 *       specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * @package	is_email
 * @author	Dominic Sayers <dominic@sayers.cc>
 * @copyright	2008-2016 Dominic Sayers
 * @license	https://www.opensource.org/licenses/bsd-license.php BSD License
 * @link	https://www.dominicsayers.com/isemail
 * @version	3.0.7 - Changed my link to https://isemail.info throughout
 */

// The quality of this code has been improved greatly by using PHPLint
// Copyright (c) 2010 Umberto Salsi
// This is free software; see the license for copying conditions.
// More info: https://www.icosaedro.it/phplint/
/*.
	require_module 'standard';
	require_module 'pcre';
.*/

if (!defined('ISEMAIL_VALID')) {
/*:diagnostic constants start:*/
// This part of the code is generated using data from test/meta.xml. Beware of making manual alterations
	// Categories
	define('ISEMAIL_VALID_CATEGORY', 1);
	define('ISEMAIL_DNSWARN', 7);
	define('ISEMAIL_RFC5321', 15);
	define('ISEMAIL_CFWS', 31);
	define('ISEMAIL_DEPREC', 63);
	define('ISEMAIL_RFC5322', 127);
	define('ISEMAIL_ERR', 255);

	// Diagnoses
	// Address is valid
	define('ISEMAIL_VALID', 0);
	// Address is valid but a DNS check was not successful
	define('ISEMAIL_DNSWARN_NO_MX_RECORD', 5);
	define('ISEMAIL_DNSWARN_NO_RECORD', 6);
	// Address is valid for SMTP but has unusual elements
	define('ISEMAIL_RFC5321_TLD', 9);
	define('ISEMAIL_RFC5321_TLDNUMERIC', 10);
	define('ISEMAIL_RFC5321_QUOTEDSTRING', 11);
	define('ISEMAIL_RFC5321_ADDRESSLITERAL', 12);
	define('ISEMAIL_RFC5321_IPV6DEPRECATED', 13);
	// Address is valid within the message but cannot be used unmodified for the envelope
	define('ISEMAIL_CFWS_COMMENT', 17);
	define('ISEMAIL_CFWS_FWS', 18);
	// Address contains deprecated elements but may still be valid in restricted contexts
	define('ISEMAIL_DEPREC_LOCALPART', 33);
	define('ISEMAIL_DEPREC_FWS', 34);
	define('ISEMAIL_DEPREC_QTEXT', 35);
	define('ISEMAIL_DEPREC_QP', 36);
	define('ISEMAIL_DEPREC_COMMENT', 37);
	define('ISEMAIL_DEPREC_CTEXT', 38);
	define('ISEMAIL_DEPREC_CFWS_NEAR_AT', 49);
	// The address is only valid according to the broad definition of RFC 5322. It is otherwise invalid.
	define('ISEMAIL_RFC5322_DOMAIN', 65);
	define('ISEMAIL_RFC5322_TOOLONG', 66);
	define('ISEMAIL_RFC5322_LOCAL_TOOLONG', 67);
	define('ISEMAIL_RFC5322_DOMAIN_TOOLONG', 68);
	define('ISEMAIL_RFC5322_LABEL_TOOLONG', 69);
	define('ISEMAIL_RFC5322_DOMAINLITERAL', 70);
	define('ISEMAIL_RFC5322_DOMLIT_OBSDTEXT', 71);
	define('ISEMAIL_RFC5322_IPV6_GRPCOUNT', 72);
	define('ISEMAIL_RFC5322_IPV6_2X2XCOLON', 73);
	define('ISEMAIL_RFC5322_IPV6_BADCHAR', 74);
	define('ISEMAIL_RFC5322_IPV6_MAXGRPS', 75);
	define('ISEMAIL_RFC5322_IPV6_COLONSTRT', 76);
	define('ISEMAIL_RFC5322_IPV6_COLONEND', 77);
	// Address is invalid for any purpose
	define('ISEMAIL_ERR_EXPECTING_DTEXT', 129);
	define('ISEMAIL_ERR_NOLOCALPART', 130);
	define('ISEMAIL_ERR_NODOMAIN', 131);
	define('ISEMAIL_ERR_CONSECUTIVEDOTS', 132);
	define('ISEMAIL_ERR_ATEXT_AFTER_CFWS', 133);
	define('ISEMAIL_ERR_ATEXT_AFTER_QS', 134);
	define('ISEMAIL_ERR_ATEXT_AFTER_DOMLIT', 135);
	define('ISEMAIL_ERR_EXPECTING_QPAIR', 136);
	define('ISEMAIL_ERR_EXPECTING_ATEXT', 137);
	define('ISEMAIL_ERR_EXPECTING_QTEXT', 138);
	define('ISEMAIL_ERR_EXPECTING_CTEXT', 139);
	define('ISEMAIL_ERR_BACKSLASHEND', 140);
	define('ISEMAIL_ERR_DOT_START', 141);
	define('ISEMAIL_ERR_DOT_END', 142);
	define('ISEMAIL_ERR_DOMAINHYPHENSTART', 143);
	define('ISEMAIL_ERR_DOMAINHYPHENEND', 144);
	define('ISEMAIL_ERR_UNCLOSEDQUOTEDSTR', 145);
	define('ISEMAIL_ERR_UNCLOSEDCOMMENT', 146);
	define('ISEMAIL_ERR_UNCLOSEDDOMLIT', 147);
	define('ISEMAIL_ERR_FWS_CRLF_X2', 148);
	define('ISEMAIL_ERR_FWS_CRLF_END', 149);
	define('ISEMAIL_ERR_CR_NO_LF', 150);
// End of generated code
/*:diagnostic constants end:*/

	// function control
	define('ISEMAIL_THRESHOLD'		, 16);

	// Email parts
	define('ISEMAIL_COMPONENT_LOCALPART'	, 0);
	define('ISEMAIL_COMPONENT_DOMAIN'	, 1);
	define('ISEMAIL_COMPONENT_LITERAL'	, 2);
	define('ISEMAIL_CONTEXT_COMMENT'	, 3);
	define('ISEMAIL_CONTEXT_FWS'		, 4);
	define('ISEMAIL_CONTEXT_QUOTEDSTRING'	, 5);
	define('ISEMAIL_CONTEXT_QUOTEDPAIR'	, 6);

	// Miscellaneous string constants
	define('ISEMAIL_STRING_AT'		, '@');
	define('ISEMAIL_STRING_BACKSLASH'	, '\\');
	define('ISEMAIL_STRING_DOT'		, '.');
	define('ISEMAIL_STRING_DQUOTE'		, '"');
	define('ISEMAIL_STRING_OPENPARENTHESIS'	, '(');
	define('ISEMAIL_STRING_CLOSEPARENTHESIS', ')');
	define('ISEMAIL_STRING_OPENSQBRACKET'	, '[');
	define('ISEMAIL_STRING_CLOSESQBRACKET'	, ']');
	define('ISEMAIL_STRING_HYPHEN'		, '-');
	define('ISEMAIL_STRING_COLON'		, ':');
	define('ISEMAIL_STRING_DOUBLECOLON'	, '::');
	define('ISEMAIL_STRING_SP'		, ' ');
	define('ISEMAIL_STRING_HTAB'		, "\t");
	define('ISEMAIL_STRING_CR'		, "\r");
	define('ISEMAIL_STRING_LF'		, "\n");
	define('ISEMAIL_STRING_IPV6TAG'		, 'IPv6:');
	// US-ASCII visible characters not valid for atext (https://tools.ietf.org/html/rfc5322#section-3.2.3)
	define('ISEMAIL_STRING_SPECIALS'	, '()<>[]:;@\\,."');
}

/**
 * Check that an email address conforms to RFCs 5321, 5322 and others
 *
 * As of Version 3.0, we are now distinguishing clearly between a Mailbox
 * as defined by RFC 5321 and an addr-spec as defined by RFC 5322. Depending
 * on the context, either can be regarded as a valid email address. The
 * RFC 5321 Mailbox specification is more restrictive (comments, white space
 * and obsolete forms are not allowed)
 *
 * @param string	$email		The email address to check
 * @param boolean	$checkDNS	If true then a DNS check for MX records will be made
 * @param mixed		$errorlevel	Determines the boundary between valid and invalid addresses.
 * 					Status codes above this number will be returned as-is,
 * 					status codes below will be returned as ISEMAIL_VALID. Thus the
 * 					calling program can simply look for ISEMAIL_VALID if it is
 * 					only interested in whether an address is valid or not. The
 * 					errorlevel will determine how "picky" is_email() is about
 * 					the address.
 *
 * 					If omitted or passed as false then is_email() will return
 * 					true or false rather than an integer error or warning.
 *
 * 					NB Note the difference between $errorlevel = false and
 * 					$errorlevel = 0
 * @param array		$parsedata	If passed, returns the parsed address components
 */
/*.mixed.*/ function is_email($email, $checkDNS = false, $errorlevel = false, &$parsedata = array()) {
	// Check that $email is a valid address. Read the following RFCs to understand the constraints:
	// 	(https://tools.ietf.org/html/rfc5321)
	// 	(https://tools.ietf.org/html/rfc5322)
	// 	(https://tools.ietf.org/html/rfc4291#section-2.2)
	// 	(https://tools.ietf.org/html/rfc1123#section-2.1)
	// 	(https://tools.ietf.org/html/rfc3696) (guidance only)
// version 2.0: Enhance $diagnose parameter to $errorlevel
// version 3.0: Introduced status categories
// revision 3.01: BUG: $parsedata was passed by value instead of by reference

	if (is_bool($errorlevel)) {
		$threshold	= ISEMAIL_VALID;
		$diagnose	= (bool) $errorlevel;
	} else {
		$diagnose	= true;

		switch ((int) $errorlevel) {
		case E_WARNING:	$threshold	= ISEMAIL_THRESHOLD;	break;	// For backward compatibility
		case E_ERROR:	$threshold	= ISEMAIL_VALID;	break;	// For backward compatibility
		default:	$threshold	= (int) $errorlevel;
		}
	}

	$return_status = array(ISEMAIL_VALID);

	// Parse the address into components, character by character
	$raw_length	= strlen($email);
	$context	= ISEMAIL_COMPONENT_LOCALPART;	// Where we are
	$context_stack	= array($context);		// Where we have been
	$context_prior	= ISEMAIL_COMPONENT_LOCALPART;	// Where we just came from
	$token		= '';				// The current character
	$token_prior	= '';				// The previous character
	$parsedata	= array(
				ISEMAIL_COMPONENT_LOCALPART	=> '',
				ISEMAIL_COMPONENT_DOMAIN	=> ''
			       );			// For the components of the address

	$atomlist	= array(
				ISEMAIL_COMPONENT_LOCALPART	=> array(''),
				ISEMAIL_COMPONENT_DOMAIN	=> array('')
			       );			// For the dot-atom elements of the address
	$element_count	= 0;
	$element_len	= 0;
	$hyphen_flag	= false;			// Hyphen cannot occur at the end of a subdomain
	$end_or_die	= false;			// CFWS can only appear at the end of the element

//-echo "<table style=\"clear:left;\">"; // debug
	for ($i = 0; $i < $raw_length; $i++) {
		$token = $email[$i];
//-echo "<tr><td><strong>$context|",(($end_or_die) ? 'true' : 'false'),"|$token|" . max($return_status) . "</strong></td>"; // debug

		switch ($context) {
		//-------------------------------------------------------------
		// local-part
		//-------------------------------------------------------------
		case ISEMAIL_COMPONENT_LOCALPART:
			// https://tools.ietf.org/html/rfc5322#section-3.4.1
			//   local-part      =   dot-atom / quoted-string / obs-local-part
			//
			//   dot-atom        =   [CFWS] dot-atom-text [CFWS]
			//
			//   dot-atom-text   =   1*atext *("." 1*atext)
			//
			//   quoted-string   =   [CFWS]
			//                       DQUOTE *([FWS] qcontent) [FWS] DQUOTE
			//                       [CFWS]
			//
			//   obs-local-part  =   word *("." word)
			//
			//   word            =   atom / quoted-string
			//
			//   atom            =   [CFWS] 1*atext [CFWS]
			switch ($token) {
			// Comment
			case ISEMAIL_STRING_OPENPARENTHESIS:
				if ($element_len === 0)
					// Comments are OK at the beginning of an element
					$return_status[]	= ($element_count === 0) ? ISEMAIL_CFWS_COMMENT : ISEMAIL_DEPREC_COMMENT;
				else {
					$return_status[]	= ISEMAIL_CFWS_COMMENT;
					$end_or_die		= true;	// We can't start a comment in the middle of an element, so this better be the end
				}

				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_COMMENT;
				break;
			// Next dot-atom element
			case ISEMAIL_STRING_DOT:
				if ($element_len === 0)
					// Another dot, already?
					$return_status[] = ($element_count === 0) ? ISEMAIL_ERR_DOT_START : ISEMAIL_ERR_CONSECUTIVEDOTS;	// Fatal error
				else
					// The entire local-part can be a quoted string for RFC 5321
					// If it's just one atom that is quoted then it's an RFC 5322 obsolete form
					if ($end_or_die) $return_status[] = ISEMAIL_DEPREC_LOCALPART;

					$end_or_die	= false;	// CFWS & quoted strings are OK again now we're at the beginning of an element (although they are obsolete forms)
					$element_len	= 0;
					$element_count++;
					$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= $token;
					$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	= '';

				break;
			// Quoted string
			case ISEMAIL_STRING_DQUOTE:
				if ($element_len === 0) {
					// The entire local-part can be a quoted string for RFC 5321
					// If it's just one atom that is quoted then it's an RFC 5322 obsolete form
					$return_status[]	= ($element_count === 0) ? ISEMAIL_RFC5321_QUOTEDSTRING : ISEMAIL_DEPREC_LOCALPART;

					$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= $token;
					$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	.= $token;
					$element_len++;
					$end_or_die		= true;	// Quoted string must be the entire element
					$context_stack[]	= $context;
					$context		= ISEMAIL_CONTEXT_QUOTEDSTRING;
				} else {
					$return_status[]	= ISEMAIL_ERR_EXPECTING_ATEXT;	// Fatal error
				}

				break;
			// Folding White Space
			case ISEMAIL_STRING_CR:
			case ISEMAIL_STRING_SP:
			case ISEMAIL_STRING_HTAB:
				if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;	break;}	// Fatal error

				if ($element_len === 0)
					$return_status[] = ($element_count === 0) ? ISEMAIL_CFWS_FWS : ISEMAIL_DEPREC_FWS;
				else
					$end_or_die = true;	// We can't start FWS in the middle of an element, so this better be the end

				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_FWS;
				$token_prior		= $token;

				break;
			// @
			case ISEMAIL_STRING_AT:
				// At this point we should have a valid local-part
				if (count($context_stack) !== 1) die('Unexpected item on context stack');

				if	($parsedata[ISEMAIL_COMPONENT_LOCALPART] === '')
								$return_status[]	= ISEMAIL_ERR_NOLOCALPART;	// Fatal error
				elseif	($element_len === 0)	$return_status[]	= ISEMAIL_ERR_DOT_END;	// Fatal error
				// https://tools.ietf.org/html/rfc5321#section-4.5.3.1.1
				//   The maximum total length of a user name or other local-part is 64
				//   octets.
				elseif	(strlen($parsedata[ISEMAIL_COMPONENT_LOCALPART]) > 64)
								$return_status[]	= ISEMAIL_RFC5322_LOCAL_TOOLONG;
				// https://tools.ietf.org/html/rfc5322#section-3.4.1
				//   Comments and folding white space
				//   SHOULD NOT be used around the "@" in the addr-spec.
				//
				// https://tools.ietf.org/html/rfc2119
				// 4. SHOULD NOT   This phrase, or the phrase "NOT RECOMMENDED" mean that
				//    there may exist valid reasons in particular circumstances when the
				//    particular behavior is acceptable or even useful, but the full
				//    implications should be understood and the case carefully weighed
				//    before implementing any behavior described with this label.
				elseif	(($context_prior === ISEMAIL_CONTEXT_COMMENT) || ($context_prior === ISEMAIL_CONTEXT_FWS))
								$return_status[]	= ISEMAIL_DEPREC_CFWS_NEAR_AT;

				// Clear everything down for the domain parsing
				$context	= ISEMAIL_COMPONENT_DOMAIN;	// Where we are
				$context_stack	= array($context);		// Where we have been
				$element_count	= 0;
				$element_len	= 0;
				$end_or_die	= false;			// CFWS can only appear at the end of the element

				break;
			// atext
			default:
				// https://tools.ietf.org/html/rfc5322#section-3.2.3
				//    atext           =   ALPHA / DIGIT /    ; Printable US-ASCII
				//                        "!" / "#" /        ;  characters not including
				//                        "$" / "%" /        ;  specials.  Used for atoms.
				//                        "&" / "'" /
				//                        "*" / "+" /
				//                        "-" / "/" /
				//                        "=" / "?" /
				//                        "^" / "_" /
				//                        "`" / "{" /
				//                        "|" / "}" /
				//                        "~"
				if ($end_or_die) {
					// We have encountered atext where it is no longer valid
					switch ($context_prior) {
					case ISEMAIL_CONTEXT_COMMENT:
					case ISEMAIL_CONTEXT_FWS:
						$return_status[]	= ISEMAIL_ERR_ATEXT_AFTER_CFWS;
						break;
					case ISEMAIL_CONTEXT_QUOTEDSTRING:
						$return_status[]	= ISEMAIL_ERR_ATEXT_AFTER_QS;
						break;
					default:
						die ("More atext found where none is allowed, but unrecognised prior context: $context_prior");
					}
				} else {
					$context_prior	= $context;
					$ord		= ord($token);

					if (($ord < 33) || ($ord > 126) || ($ord === 10) || (!is_bool(strpos(ISEMAIL_STRING_SPECIALS, $token))))
						$return_status[]	= ISEMAIL_ERR_EXPECTING_ATEXT;	// Fatal error

					$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= $token;
					$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	.= $token;
					$element_len++;
				}
			}

			break;
		//-------------------------------------------------------------
		// Domain
		//-------------------------------------------------------------
		case ISEMAIL_COMPONENT_DOMAIN:
			// https://tools.ietf.org/html/rfc5322#section-3.4.1
			//   domain          =   dot-atom / domain-literal / obs-domain
			//
			//   dot-atom        =   [CFWS] dot-atom-text [CFWS]
			//
			//   dot-atom-text   =   1*atext *("." 1*atext)
			//
			//   domain-literal  =   [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
			//
			//   dtext           =   %d33-90 /          ; Printable US-ASCII
			//                       %d94-126 /         ;  characters not including
			//                       obs-dtext          ;  "[", "]", or "\"
			//
			//   obs-domain      =   atom *("." atom)
			//
			//   atom            =   [CFWS] 1*atext [CFWS]


			// https://tools.ietf.org/html/rfc5321#section-4.1.2
			//   Mailbox        = Local-part "@" ( Domain / address-literal )
			//
			//   Domain         = sub-domain *("." sub-domain)
			//
			//   address-literal  = "[" ( IPv4-address-literal /
			//                    IPv6-address-literal /
			//                    General-address-literal ) "]"
			//                    ; See Section 4.1.3

			// https://tools.ietf.org/html/rfc5322#section-3.4.1
			//      Note: A liberal syntax for the domain portion of addr-spec is
			//      given here.  However, the domain portion contains addressing
			//      information specified by and used in other protocols (e.g.,
			//      [RFC1034], [RFC1035], [RFC1123], [RFC5321]).  It is therefore
			//      incumbent upon implementations to conform to the syntax of
			//      addresses for the context in which they are used.
			// is_email() author's note: it's not clear how to interpret this in
			// the context of a general email address validator. The conclusion I
			// have reached is this: "addressing information" must comply with
			// RFC 5321 (and in turn RFC 1035), anything that is "semantically
			// invisible" must comply only with RFC 5322.
			switch ($token) {
			// Comment
			case ISEMAIL_STRING_OPENPARENTHESIS:
				if ($element_len === 0)
					// Comments at the start of the domain are deprecated in the text
					// Comments at the start of a subdomain are obs-domain
					// (https://tools.ietf.org/html/rfc5322#section-3.4.1)
					$return_status[]	= ($element_count === 0) ? ISEMAIL_DEPREC_CFWS_NEAR_AT : ISEMAIL_DEPREC_COMMENT;
				else {
					$return_status[]	= ISEMAIL_CFWS_COMMENT;
					$end_or_die		= true;	// We can't start a comment in the middle of an element, so this better be the end
				}

				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_COMMENT;
				break;
			// Next dot-atom element
			case ISEMAIL_STRING_DOT:
				if ($element_len === 0)
					// Another dot, already?
					$return_status[]	= ($element_count === 0) ? ISEMAIL_ERR_DOT_START : ISEMAIL_ERR_CONSECUTIVEDOTS;	// Fatal error
				elseif ($hyphen_flag)
					// Previous subdomain ended in a hyphen
					$return_status[]	= ISEMAIL_ERR_DOMAINHYPHENEND;	// Fatal error
				else
					// Nowhere in RFC 5321 does it say explicitly that the
					// domain part of a Mailbox must be a valid domain according
					// to the DNS standards set out in RFC 1035, but this *is*
					// implied in several places. For instance, wherever the idea
					// of host routing is discussed the RFC says that the domain
					// must be looked up in the DNS. This would be nonsense unless
					// the domain was designed to be a valid DNS domain. Hence we
					// must conclude that the RFC 1035 restriction on label length
					// also applies to RFC 5321 domains.
					//
					// https://tools.ietf.org/html/rfc1035#section-2.3.4
					// labels          63 octets or less
					if ($element_len > 63) $return_status[]	= ISEMAIL_RFC5322_LABEL_TOOLONG;

					$end_or_die		= false;	// CFWS is OK again now we're at the beginning of an element (although it may be obsolete CFWS)
					$element_len		= 0;
					$element_count++;
					$atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]	= '';
					$parsedata[ISEMAIL_COMPONENT_DOMAIN]			.= $token;

				break;
			// Domain literal
			case ISEMAIL_STRING_OPENSQBRACKET:
				if ($parsedata[ISEMAIL_COMPONENT_DOMAIN] === '') {
					$end_or_die		= true;	// Domain literal must be the only component
					$element_len++;
					$context_stack[]	= $context;
					$context		= ISEMAIL_COMPONENT_LITERAL;
					$parsedata[ISEMAIL_COMPONENT_DOMAIN]			.= $token;
					$atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]	.= $token;
					$parsedata[ISEMAIL_COMPONENT_LITERAL]			= '';
				} else {
					$return_status[]	= ISEMAIL_ERR_EXPECTING_ATEXT;	// Fatal error
				}

				break;
			// Folding White Space
			case ISEMAIL_STRING_CR:
			case ISEMAIL_STRING_SP:
			case ISEMAIL_STRING_HTAB:
				if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;	break;}	// Fatal error

				if ($element_len === 0)
					$return_status[]	= ($element_count === 0) ? ISEMAIL_DEPREC_CFWS_NEAR_AT : ISEMAIL_DEPREC_FWS;
				else {
					$return_status[]	= ISEMAIL_CFWS_FWS;
					$end_or_die	= true;	// We can't start FWS in the middle of an element, so this better be the end
				}

				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_FWS;
				$token_prior		= $token;
				break;
			// atext
			default:
				// RFC 5322 allows any atext...
				// https://tools.ietf.org/html/rfc5322#section-3.2.3
				//    atext           =   ALPHA / DIGIT /    ; Printable US-ASCII
				//                        "!" / "#" /        ;  characters not including
				//                        "$" / "%" /        ;  specials.  Used for atoms.
				//                        "&" / "'" /
				//                        "*" / "+" /
				//                        "-" / "/" /
				//                        "=" / "?" /
				//                        "^" / "_" /
				//                        "`" / "{" /
				//                        "|" / "}" /
				//                        "~"

				// But RFC 5321 only allows letter-digit-hyphen to comply with DNS rules (RFCs 1034 & 1123)
				// https://tools.ietf.org/html/rfc5321#section-4.1.2
				//   sub-domain     = Let-dig [Ldh-str]
				//
				//   Let-dig        = ALPHA / DIGIT
				//
				//   Ldh-str        = *( ALPHA / DIGIT / "-" ) Let-dig
				//
				if ($end_or_die) {
					// We have encountered atext where it is no longer valid
					switch ($context_prior) {
					case ISEMAIL_CONTEXT_COMMENT:
					case ISEMAIL_CONTEXT_FWS:
						$return_status[]	= ISEMAIL_ERR_ATEXT_AFTER_CFWS;
						break;
					case ISEMAIL_COMPONENT_LITERAL:
						$return_status[]	= ISEMAIL_ERR_ATEXT_AFTER_DOMLIT;
						break;
					default:
						die ("More atext found where none is allowed, but unrecognised prior context: $context_prior");
					}
				}

				$ord		= ord($token);
				$hyphen_flag	= false;	// Assume this token isn't a hyphen unless we discover it is

				if (($ord < 33) || ($ord > 126) || (!is_bool(strpos(ISEMAIL_STRING_SPECIALS, $token)))) {
					$return_status[]	= ISEMAIL_ERR_EXPECTING_ATEXT;	// Fatal error
				} elseif ($token === ISEMAIL_STRING_HYPHEN) {
					if ($element_len === 0) {
						// Hyphens can't be at the beginning of a subdomain
						$return_status[]	= ISEMAIL_ERR_DOMAINHYPHENSTART;	// Fatal error
					}

					$hyphen_flag = true;
				} elseif (!(($ord > 47 && $ord < 58) || ($ord > 64 && $ord < 91) || ($ord > 96 && $ord < 123))) {
					// Not an RFC 5321 subdomain, but still OK by RFC 5322
					$return_status[]	= ISEMAIL_RFC5322_DOMAIN;
				}

				$parsedata[ISEMAIL_COMPONENT_DOMAIN]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]	.= $token;
				$element_len++;
			}

			break;
		//-------------------------------------------------------------
		// Domain literal
		//-------------------------------------------------------------
		case ISEMAIL_COMPONENT_LITERAL:
			// https://tools.ietf.org/html/rfc5322#section-3.4.1
			//   domain-literal  =   [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
			//
			//   dtext           =   %d33-90 /          ; Printable US-ASCII
			//                       %d94-126 /         ;  characters not including
			//                       obs-dtext          ;  "[", "]", or "\"
			//
			//   obs-dtext       =   obs-NO-WS-CTL / quoted-pair
			switch ($token) {
			// End of domain literal
			case ISEMAIL_STRING_CLOSESQBRACKET:
				if ((int) max($return_status) < ISEMAIL_DEPREC) {
					// Could be a valid RFC 5321 address literal, so let's check

					// https://tools.ietf.org/html/rfc5321#section-4.1.2
					//   address-literal  = "[" ( IPv4-address-literal /
					//                    IPv6-address-literal /
					//                    General-address-literal ) "]"
					//                    ; See Section 4.1.3
					//
					// https://tools.ietf.org/html/rfc5321#section-4.1.3
					//   IPv4-address-literal  = Snum 3("."  Snum)
					//
					//   IPv6-address-literal  = "IPv6:" IPv6-addr
					//
					//   General-address-literal  = Standardized-tag ":" 1*dcontent
					//
					//   Standardized-tag  = Ldh-str
					//                     ; Standardized-tag MUST be specified in a
					//                     ; Standards-Track RFC and registered with IANA
					//
					//   dcontent       = %d33-90 / ; Printable US-ASCII
					//                  %d94-126 ; excl. "[", "\", "]"
					//
					//   Snum           = 1*3DIGIT
					//                  ; representing a decimal integer
					//                  ; value in the range 0 through 255
					//
					//   IPv6-addr      = IPv6-full / IPv6-comp / IPv6v4-full / IPv6v4-comp
					//
					//   IPv6-hex       = 1*4HEXDIG
					//
					//   IPv6-full      = IPv6-hex 7(":" IPv6-hex)
					//
					//   IPv6-comp      = [IPv6-hex *5(":" IPv6-hex)] "::"
					//                  [IPv6-hex *5(":" IPv6-hex)]
					//                  ; The "::" represents at least 2 16-bit groups of
					//                  ; zeros.  No more than 6 groups in addition to the
					//                  ; "::" may be present.
					//
					//   IPv6v4-full    = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal
					//
					//   IPv6v4-comp    = [IPv6-hex *3(":" IPv6-hex)] "::"
					//                  [IPv6-hex *3(":" IPv6-hex) ":"]
					//                  IPv4-address-literal
					//                  ; The "::" represents at least 2 16-bit groups of
					//                  ; zeros.  No more than 4 groups in addition to the
					//                  ; "::" and IPv4-address-literal may be present.
					//
					// is_email() author's note: We can't use ip2long() to validate
					// IPv4 addresses because it accepts abbreviated addresses
					// (xxx.xxx.xxx), expanding the last group to complete the address.
					// filter_var() validates IPv6 address inconsistently (up to PHP 5.3.3
					// at least) -- see https://bugs.php.net/bug.php?id=53236 for example
					$max_groups	= 8;
					$matchesIP	= array();
			/*.mixed.*/	$index		= false;
					$addressliteral	= $parsedata[ISEMAIL_COMPONENT_LITERAL];

					// Extract IPv4 part from the end of the address-literal (if there is one)
					if (preg_match('/\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/', $addressliteral, $matchesIP) > 0) {
						$index = strrpos($addressliteral, $matchesIP[0]);
						if ($index !== 0) $addressliteral = substr($addressliteral, 0, $index) . '0:0'; // Convert IPv4 part to IPv6 format for further testing
					}

					if ($index === 0) {
						// Nothing there except a valid IPv4 address, so...
						$return_status[]	= ISEMAIL_RFC5321_ADDRESSLITERAL;
					} elseif (strncasecmp($addressliteral, ISEMAIL_STRING_IPV6TAG, 5) !== 0) {
						$return_status[]	= ISEMAIL_RFC5322_DOMAINLITERAL;
					} else {
						$IPv6		= substr($addressliteral, 5);
						$matchesIP	= explode(ISEMAIL_STRING_COLON, $IPv6);	// Revision 2.7: Daniel Marschall's new IPv6 testing strategy
						$groupCount	= count($matchesIP);
						$index		= strpos($IPv6,ISEMAIL_STRING_DOUBLECOLON);

						if ($index === false) {
							// We need exactly the right number of groups
							if ($groupCount !== $max_groups)
								$return_status[]	= ISEMAIL_RFC5322_IPV6_GRPCOUNT;
						} else {
							if ($index !== strrpos($IPv6,ISEMAIL_STRING_DOUBLECOLON))
								$return_status[]	= ISEMAIL_RFC5322_IPV6_2X2XCOLON;
							else {
								if ($index === 0 || $index === (strlen($IPv6) - 2)) $max_groups++;	// RFC 4291 allows :: at the start or end of an address with 7 other groups in addition

								if ($groupCount > $max_groups)
									$return_status[]	= ISEMAIL_RFC5322_IPV6_MAXGRPS;
								elseif ($groupCount === $max_groups)
									$return_status[]	= ISEMAIL_RFC5321_IPV6DEPRECATED;	// Eliding a single "::"
							}
						}

						// Revision 2.7: Daniel Marschall's new IPv6 testing strategy
						if ((substr($IPv6, 0,  1) === ISEMAIL_STRING_COLON) && (substr($IPv6, 1,  1) !== ISEMAIL_STRING_COLON))
							$return_status[]	= ISEMAIL_RFC5322_IPV6_COLONSTRT;	// Address starts with a single colon
						elseif ((substr($IPv6, -1) === ISEMAIL_STRING_COLON) && (substr($IPv6, -2, 1) !== ISEMAIL_STRING_COLON))
							$return_status[]	= ISEMAIL_RFC5322_IPV6_COLONEND;	// Address ends with a single colon
						elseif (count(preg_grep('/^[0-9A-Fa-f]{0,4}$/', $matchesIP, PREG_GREP_INVERT)) !== 0)
							$return_status[]	= ISEMAIL_RFC5322_IPV6_BADCHAR;	// Check for unmatched characters
						else
							$return_status[]	= ISEMAIL_RFC5321_ADDRESSLITERAL;
					}
				} else
					$return_status[]	= ISEMAIL_RFC5322_DOMAINLITERAL;


				$parsedata[ISEMAIL_COMPONENT_DOMAIN]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]	.= $token;
				$element_len++;
				$context_prior		= $context;
				$context		= (int) array_pop($context_stack);
				break;
			case ISEMAIL_STRING_BACKSLASH:
				$return_status[]	= ISEMAIL_RFC5322_DOMLIT_OBSDTEXT;
				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_QUOTEDPAIR;
				break;
			// Folding White Space
			case ISEMAIL_STRING_CR:
			case ISEMAIL_STRING_SP:
			case ISEMAIL_STRING_HTAB:
				if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;	break;}	// Fatal error

				$return_status[]	= ISEMAIL_CFWS_FWS;

				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_FWS;
				$token_prior		= $token;
				break;
			// dtext
			default:
				// https://tools.ietf.org/html/rfc5322#section-3.4.1
				//   dtext           =   %d33-90 /          ; Printable US-ASCII
				//                       %d94-126 /         ;  characters not including
				//                       obs-dtext          ;  "[", "]", or "\"
				//
				//   obs-dtext       =   obs-NO-WS-CTL / quoted-pair
				//
				//   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
				//                       %d11 /             ;  characters that do not
				//                       %d12 /             ;  include the carriage
				//                       %d14-31 /          ;  return, line feed, and
				//                       %d127              ;  white space characters
				$ord = ord($token);

				// CR, LF, SP & HTAB have already been parsed above
				if (($ord > 127) || ($ord === 0) || ($token === ISEMAIL_STRING_OPENSQBRACKET)) {
					$return_status[]	= ISEMAIL_ERR_EXPECTING_DTEXT;	// Fatal error
					break;
				} elseif (($ord < 33) || ($ord === 127)) {
					$return_status[]	= ISEMAIL_RFC5322_DOMLIT_OBSDTEXT;
				}

				$parsedata[ISEMAIL_COMPONENT_LITERAL]			.= $token;
				$parsedata[ISEMAIL_COMPONENT_DOMAIN]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]	.= $token;
				$element_len++;
			}

			break;
		//-------------------------------------------------------------
		// Quoted string
		//-------------------------------------------------------------
		case ISEMAIL_CONTEXT_QUOTEDSTRING:
			// https://tools.ietf.org/html/rfc5322#section-3.2.4
			//   quoted-string   =   [CFWS]
			//                       DQUOTE *([FWS] qcontent) [FWS] DQUOTE
			//                       [CFWS]
			//
			//   qcontent        =   qtext / quoted-pair
			switch ($token) {
			// Quoted pair
			case ISEMAIL_STRING_BACKSLASH:
				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_QUOTEDPAIR;
				break;
			// Folding White Space
			// Inside a quoted string, spaces are allowed as regular characters.
			// It's only FWS if we include HTAB or CRLF
			case ISEMAIL_STRING_CR:
			case ISEMAIL_STRING_HTAB:
				if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;	break;}	// Fatal error

				// https://tools.ietf.org/html/rfc5322#section-3.2.2
				//   Runs of FWS, comment, or CFWS that occur between lexical tokens in a
				//   structured header field are semantically interpreted as a single
				//   space character.

				// https://tools.ietf.org/html/rfc5322#section-3.2.4
				//   the CRLF in any FWS/CFWS that appears within the quoted-string [is]
				//   semantically "invisible" and therefore not part of the quoted-string
				$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= ISEMAIL_STRING_SP;
				$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	.= ISEMAIL_STRING_SP;
				$element_len++;

				$return_status[]		= ISEMAIL_CFWS_FWS;
				$context_stack[]		= $context;
				$context			= ISEMAIL_CONTEXT_FWS;
				$token_prior			= $token;
				break;
			// End of quoted string
			case ISEMAIL_STRING_DQUOTE:
				$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	.= $token;
				$element_len++;
				$context_prior			= $context;
				$context			= (int) array_pop($context_stack);
				break;
			// qtext
			default:
				// https://tools.ietf.org/html/rfc5322#section-3.2.4
				//   qtext           =   %d33 /             ; Printable US-ASCII
				//                       %d35-91 /          ;  characters not including
				//                       %d93-126 /         ;  "\" or the quote character
				//                       obs-qtext
				//
				//   obs-qtext       =   obs-NO-WS-CTL
				//
				//   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
				//                       %d11 /             ;  characters that do not
				//                       %d12 /             ;  include the carriage
				//                       %d14-31 /          ;  return, line feed, and
				//                       %d127              ;  white space characters
				$ord = ord($token);

				if (($ord > 127) || ($ord === 0) || ($ord === 10)) {
					$return_status[]	= ISEMAIL_ERR_EXPECTING_QTEXT;	// Fatal error
				} elseif (($ord < 32) || ($ord === 127))
					$return_status[]	= ISEMAIL_DEPREC_QTEXT;

				$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	.= $token;
				$element_len++;
			}

			// https://tools.ietf.org/html/rfc5322#section-3.4.1
			//   If the
			//   string can be represented as a dot-atom (that is, it contains no
			//   characters other than atext characters or "." surrounded by atext
			//   characters), then the dot-atom form SHOULD be used and the quoted-
			//   string form SHOULD NOT be used.
// To do
			break;
		//-------------------------------------------------------------
		// Quoted pair
		//-------------------------------------------------------------
		case ISEMAIL_CONTEXT_QUOTEDPAIR:
			// https://tools.ietf.org/html/rfc5322#section-3.2.1
			//   quoted-pair     =   ("\" (VCHAR / WSP)) / obs-qp
			//
			//   VCHAR           =  %d33-126            ; visible (printing) characters
			//   WSP             =  SP / HTAB           ; white space
			//
			//   obs-qp          =   "\" (%d0 / obs-NO-WS-CTL / LF / CR)
			//
			//   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
			//                       %d11 /             ;  characters that do not
			//                       %d12 /             ;  include the carriage
			//                       %d14-31 /          ;  return, line feed, and
			//                       %d127              ;  white space characters
			//
			// i.e. obs-qp       =  "\" (%d0-8, %d10-31 / %d127)
			$ord = ord($token);

			if	($ord > 127)
					$return_status[]	= ISEMAIL_ERR_EXPECTING_QPAIR;	// Fatal error
			elseif	((($ord < 31) && ($ord !== 9)) || ($ord === 127))	// SP & HTAB are allowed
					$return_status[]	= ISEMAIL_DEPREC_QP;

			// At this point we know where this qpair occurred so
			// we could check to see if the character actually
			// needed to be quoted at all.
			// https://tools.ietf.org/html/rfc5321#section-4.1.2
			//   the sending system SHOULD transmit the
			//   form that uses the minimum quoting possible.
// To do: check whether the character needs to be quoted (escaped) in this context
			$context_prior	= $context;
			$context	= (int) array_pop($context_stack);	// End of qpair
			$token		= ISEMAIL_STRING_BACKSLASH . $token;

			switch ($context) {
			case ISEMAIL_CONTEXT_COMMENT:
				break;
			case ISEMAIL_CONTEXT_QUOTEDSTRING:
				$parsedata[ISEMAIL_COMPONENT_LOCALPART]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]	.= $token;
				$element_len	+= 2;	// The maximum sizes specified by RFC 5321 are octet counts, so we must include the backslash
				break;
			case ISEMAIL_COMPONENT_LITERAL:
				$parsedata[ISEMAIL_COMPONENT_DOMAIN]			.= $token;
				$atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]	.= $token;
				$element_len	+= 2;	// The maximum sizes specified by RFC 5321 are octet counts, so we must include the backslash
				break;
			default:
				die("Quoted pair logic invoked in an invalid context: $context");
			}

			break;
		//-------------------------------------------------------------
		// Comment
		//-------------------------------------------------------------
		case ISEMAIL_CONTEXT_COMMENT:
			// https://tools.ietf.org/html/rfc5322#section-3.2.2
			//   comment         =   "(" *([FWS] ccontent) [FWS] ")"
			//
			//   ccontent        =   ctext / quoted-pair / comment
			switch ($token) {
			// Nested comment
			case ISEMAIL_STRING_OPENPARENTHESIS:
				// Nested comments are OK
				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_COMMENT;
				break;
			// End of comment
			case ISEMAIL_STRING_CLOSEPARENTHESIS:
				$context_prior		= $context;
				$context		= (int) array_pop($context_stack);

				// https://tools.ietf.org/html/rfc5322#section-3.2.2
				//   Runs of FWS, comment, or CFWS that occur between lexical tokens in a
				//   structured header field are semantically interpreted as a single
				//   space character.
				//
				// is_email() author's note: This *cannot* mean that we must add a
				// space to the address wherever CFWS appears. This would result in
				// any addr-spec that had CFWS outside a quoted string being invalid
				// for RFC 5321.
//				if (($context === ISEMAIL_COMPONENT_LOCALPART) || ($context === ISEMAIL_COMPONENT_DOMAIN)) {
//					$parsedata[$context]			.= ISEMAIL_STRING_SP;
//					$atomlist[$context][$element_count]	.= ISEMAIL_STRING_SP;
//					$element_len++;
//				}

				break;
			// Quoted pair
			case ISEMAIL_STRING_BACKSLASH:
				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_QUOTEDPAIR;
				break;
			// Folding White Space
			case ISEMAIL_STRING_CR:
			case ISEMAIL_STRING_SP:
			case ISEMAIL_STRING_HTAB:
				if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;	break;}	// Fatal error

				$return_status[]	= ISEMAIL_CFWS_FWS;

				$context_stack[]	= $context;
				$context		= ISEMAIL_CONTEXT_FWS;
				$token_prior		= $token;
				break;
			// ctext
			default:
				// https://tools.ietf.org/html/rfc5322#section-3.2.3
				//   ctext           =   %d33-39 /          ; Printable US-ASCII
				//                       %d42-91 /          ;  characters not including
				//                       %d93-126 /         ;  "(", ")", or "\"
				//                       obs-ctext
				//
				//   obs-ctext       =   obs-NO-WS-CTL
				//
				//   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
				//                       %d11 /             ;  characters that do not
				//                       %d12 /             ;  include the carriage
				//                       %d14-31 /          ;  return, line feed, and
				//                       %d127              ;  white space characters
				$ord = ord($token);

				if (($ord > 127) || ($ord === 0) || ($ord === 10)) {
					$return_status[]	= ISEMAIL_ERR_EXPECTING_CTEXT;	// Fatal error
					break;
				} elseif (($ord < 32) || ($ord === 127)) {
					$return_status[]	= ISEMAIL_DEPREC_CTEXT;
				}
			}

			break;
		//-------------------------------------------------------------
		// Folding White Space
		//-------------------------------------------------------------
		case ISEMAIL_CONTEXT_FWS:
			// https://tools.ietf.org/html/rfc5322#section-3.2.2
			//   FWS             =   ([*WSP CRLF] 1*WSP) /  obs-FWS
			//                                          ; Folding white space

			// But note the erratum:
			// https://www.rfc-editor.org/errata_search.php?rfc=5322&eid=1908:
			//   In the obsolete syntax, any amount of folding white space MAY be
			//   inserted where the obs-FWS rule is allowed.  This creates the
			//   possibility of having two consecutive "folds" in a line, and
			//   therefore the possibility that a line which makes up a folded header
			//   field could be composed entirely of white space.
			//
			//   obs-FWS         =   1*([CRLF] WSP)
			if ($token_prior === ISEMAIL_STRING_CR) {
				if ($token === ISEMAIL_STRING_CR) {
					$return_status[]	= ISEMAIL_ERR_FWS_CRLF_X2;	// Fatal error
					break;
				}

				if (isset($crlf_count)) {
					if (++$crlf_count > 1)
						$return_status[]	= ISEMAIL_DEPREC_FWS;	// Multiple folds = obsolete FWS
				} else $crlf_count = 1;
			}

			switch ($token) {
			case ISEMAIL_STRING_CR:
				if ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))
					$return_status[]	= ISEMAIL_ERR_CR_NO_LF;	// Fatal error

				break;
			case ISEMAIL_STRING_SP:
			case ISEMAIL_STRING_HTAB:
				break;
			default:
				if ($token_prior === ISEMAIL_STRING_CR) {
					$return_status[]	= ISEMAIL_ERR_FWS_CRLF_END;	// Fatal error
					break;
				}

				if (isset($crlf_count)) unset($crlf_count);

				$context_prior					= $context;
				$context					= (int) array_pop($context_stack);	// End of FWS

				// https://tools.ietf.org/html/rfc5322#section-3.2.2
				//   Runs of FWS, comment, or CFWS that occur between lexical tokens in a
				//   structured header field are semantically interpreted as a single
				//   space character.
				//
				// is_email() author's note: This *cannot* mean that we must add a
				// space to the address wherever CFWS appears. This would result in
				// any addr-spec that had CFWS outside a quoted string being invalid
				// for RFC 5321.
//				if (($context === ISEMAIL_COMPONENT_LOCALPART) || ($context === ISEMAIL_COMPONENT_DOMAIN)) {
//					$parsedata[$context]			.= ISEMAIL_STRING_SP;
//					$atomlist[$context][$element_count]	.= ISEMAIL_STRING_SP;
//					$element_len++;
//				}

				$i--;	// Look at this token again in the parent context
			}

			$token_prior = $token;
			break;
		//-------------------------------------------------------------
		// A context we aren't expecting
		//-------------------------------------------------------------
		default:
			die("Unknown context: $context");
		}

//-echo "<td>$context|",(($end_or_die) ? 'true' : 'false'),"|$token|" . max($return_status) . "</td></tr>"; // debug
		if ((int) max($return_status) > ISEMAIL_RFC5322) break;	// No point going on if we've got a fatal error
	}

	// Some simple final tests
	if ((int) max($return_status) < ISEMAIL_RFC5322) {
		if	($context 	=== ISEMAIL_CONTEXT_QUOTEDSTRING)	$return_status[]	= ISEMAIL_ERR_UNCLOSEDQUOTEDSTR;	// Fatal error
		elseif	($context 	=== ISEMAIL_CONTEXT_QUOTEDPAIR)		$return_status[]	= ISEMAIL_ERR_BACKSLASHEND;		// Fatal error
		elseif	($context 	=== ISEMAIL_CONTEXT_COMMENT)		$return_status[]	= ISEMAIL_ERR_UNCLOSEDCOMMENT;		// Fatal error
		elseif	($context 	=== ISEMAIL_COMPONENT_LITERAL)		$return_status[]	= ISEMAIL_ERR_UNCLOSEDDOMLIT;		// Fatal error
		elseif	($token		=== ISEMAIL_STRING_CR)			$return_status[]	= ISEMAIL_ERR_FWS_CRLF_END;		// Fatal error
		elseif	($parsedata[ISEMAIL_COMPONENT_DOMAIN]	=== '')		$return_status[]	= ISEMAIL_ERR_NODOMAIN;			// Fatal error
		elseif	($element_len	=== 0)					$return_status[]	= ISEMAIL_ERR_DOT_END;			// Fatal error
		elseif	($hyphen_flag)						$return_status[]	= ISEMAIL_ERR_DOMAINHYPHENEND;		// Fatal error
		// https://tools.ietf.org/html/rfc5321#section-4.5.3.1.2
		//   The maximum total length of a domain name or number is 255 octets.
		elseif	(strlen($parsedata[ISEMAIL_COMPONENT_DOMAIN]) > 255)
										$return_status[]	= ISEMAIL_RFC5322_DOMAIN_TOOLONG;
		// https://tools.ietf.org/html/rfc5321#section-4.1.2
		//   Forward-path   = Path
		//
		//   Path           = "<" [ A-d-l ":" ] Mailbox ">"
		//
		// https://tools.ietf.org/html/rfc5321#section-4.5.3.1.3
		//   The maximum total length of a reverse-path or forward-path is 256
		//   octets (including the punctuation and element separators).
		//
		// Thus, even without (obsolete) routing information, the Mailbox can
		// only be 254 characters long. This is confirmed by this verified
		// erratum to RFC 3696:
		//
		// https://www.rfc-editor.org/errata_search.php?rfc=3696&eid=1690
		//   However, there is a restriction in RFC 2821 on the length of an
		//   address in MAIL and RCPT commands of 254 characters.  Since addresses
		//   that do not fit in those fields are not normally useful, the upper
		//   limit on address lengths should normally be considered to be 254.
		elseif	(strlen($parsedata[ISEMAIL_COMPONENT_LOCALPART] . ISEMAIL_STRING_AT . $parsedata[ISEMAIL_COMPONENT_DOMAIN]) > 254)
										$return_status[]	= ISEMAIL_RFC5322_TOOLONG;
		// https://tools.ietf.org/html/rfc1035#section-2.3.4
		// labels          63 octets or less
		elseif ($element_len > 63)					$return_status[]	= ISEMAIL_RFC5322_LABEL_TOOLONG;
	}

	// Check DNS?
	$dns_checked = false;

	if ($checkDNS && ((int) max($return_status) < ISEMAIL_DNSWARN) && function_exists('dns_get_record')) {
		// https://tools.ietf.org/html/rfc5321#section-2.3.5
		//   Names that can
		//   be resolved to MX RRs or address (i.e., A or AAAA) RRs (as discussed
		//   in Section 5) are permitted, as are CNAME RRs whose targets can be
		//   resolved, in turn, to MX or address RRs.
		//
		// https://tools.ietf.org/html/rfc5321#section-5.1
		//   The lookup first attempts to locate an MX record associated with the
		//   name.  If a CNAME record is found, the resulting name is processed as
		//   if it were the initial name. ... If an empty list of MXs is returned,
		//   the address is treated as if it was associated with an implicit MX
		//   RR, with a preference of 0, pointing to that host.
		//
		// is_email() author's note: We will regard the existence of a CNAME to be
		// sufficient evidence of the domain's existence. For performance reasons
		// we will not repeat the DNS lookup for the CNAME's target, but we will
		// raise a warning because we didn't immediately find an MX record.
		if ($element_count === 0) $parsedata[ISEMAIL_COMPONENT_DOMAIN] .= '.';		// Checking TLD DNS seems to work only if you explicitly check from the root

		$result = @dns_get_record($parsedata[ISEMAIL_COMPONENT_DOMAIN], DNS_MX);	// Not using checkdnsrr because of a suspected bug in PHP 5.3 (https://bugs.php.net/bug.php?id=51844)

		if ((is_bool($result) && !(bool) $result))
			$return_status[] = ISEMAIL_DNSWARN_NO_RECORD;			// Domain can't be found in DNS
		else {
			if (count($result) === 0) {
				$return_status[]	= ISEMAIL_DNSWARN_NO_MX_RECORD;		// MX-record for domain can't be found
				$result			= @dns_get_record($parsedata[ISEMAIL_COMPONENT_DOMAIN], DNS_A + DNS_CNAME);

				if (count($result) === 0)
					$return_status[] = ISEMAIL_DNSWARN_NO_RECORD;		// No usable records for the domain can be found
			} else $dns_checked = true;
		}
	}

	// Check for TLD addresses
	// -----------------------
	// TLD addresses are specifically allowed in RFC 5321 but they are
	// unusual to say the least. We will allocate a separate
	// status to these addresses on the basis that they are more likely
	// to be typos than genuine addresses (unless we've already
	// established that the domain does have an MX record)
	//
	// https://tools.ietf.org/html/rfc5321#section-2.3.5
	//   In the case
	//   of a top-level domain used by itself in an email address, a single
	//   string is used without any dots.  This makes the requirement,
	//   described in more detail below, that only fully-qualified domain
	//   names appear in SMTP transactions on the public Internet,
	//   particularly important where top-level domains are involved.
	//
	// TLD format
	// ----------
	// The format of TLDs has changed a number of times. The standards
	// used by IANA have been largely ignored by ICANN, leading to
	// confusion over the standards being followed. These are not defined
	// anywhere, except as a general component of a DNS host name (a label).
	// However, this could potentially lead to 123.123.123.123 being a
	// valid DNS name (rather than an IP address) and thereby creating
	// an ambiguity. The most authoritative statement on TLD formats that
	// the author can find is in a (rejected!) erratum to RFC 1123
	// submitted by John Klensin, the author of RFC 5321:
	//
	// https://www.rfc-editor.org/errata_search.php?rfc=1123&eid=1353
	//   However, a valid host name can never have the dotted-decimal
	//   form #.#.#.#, since this change does not permit the highest-level
	//   component label to start with a digit even if it is not all-numeric.
	if (!$dns_checked && ((int) max($return_status) < ISEMAIL_DNSWARN)) {
		if	($element_count	=== 0)	$return_status[]	= ISEMAIL_RFC5321_TLD;

		if	(is_numeric($atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count][0]))
						$return_status[]	= ISEMAIL_RFC5321_TLDNUMERIC;
	}

	$return_status		= array_unique($return_status);
	$final_status		= (int) max($return_status);

	if (count($return_status) !== 1) array_shift($return_status); // remove redundant ISEMAIL_VALID

	$parsedata['status']	= $return_status;

	if ($final_status < $threshold) $final_status = ISEMAIL_VALID;

	return ($diagnose) ? $final_status : ($final_status < ISEMAIL_THRESHOLD);
}
?>
