85 lines
3.6 KiB
Markdown
85 lines
3.6 KiB
Markdown
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**spreadsheet-reader** is a PHP spreadsheet reader that differs from others in that the main goal for it was efficient
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data extraction that could handle large (as in really large) files. So far it may not definitely be CPU, time
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or I/O-efficient but at least it won't run out of memory (except maybe for XLS files).
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So far XLSX, ODS and text/CSV file parsing should be memory-efficient. XLS file parsing is done with php-excel-reader
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from http://code.google.com/p/php-excel-reader/ which, sadly, has memory issues with bigger spreadsheets, as it reads the
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data all at once and keeps it all in memory.
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### Requirements:
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* PHP 5.3.0 or newer
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* PHP must have Zip file support (see http://php.net/manual/en/zip.installation.php)
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### Usage:
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All data is read from the file sequentially, with each row being returned as a numeric array.
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This is about the easiest way to read a file:
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<?php
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// If you need to parse XLS files, include php-excel-reader
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require('php-excel-reader/excel_reader2.php');
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require('SpreadsheetReader.php');
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$Reader = new SpreadsheetReader('example.xlsx');
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foreach ($Reader as $Row)
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{
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print_r($Row);
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}
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?>
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However, now also multiple sheet reading is supported for file formats where it is possible. (In case of CSV, it is handled as if
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it only has one sheet.)
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You can retrieve information about sheets contained in the file by calling the `Sheets()` method which returns an array with
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sheet indexes as keys and sheet names as values. Then you can change the sheet that's currently being read by passing that index
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to the `ChangeSheet($Index)` method.
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Example:
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<?php
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$Reader = new SpreadsheetReader('example.xlsx');
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$Sheets = $Reader -> Sheets();
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foreach ($Sheets as $Index => $Name)
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{
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echo 'Sheet #'.$Index.': '.$Name;
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$Reader -> ChangeSheet($Index);
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foreach ($Reader as $Row)
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{
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print_r($Row);
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}
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}
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?>
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If a sheet is changed to the same that is currently open, the position in the file still reverts to the beginning, so as to conform
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to the same behavior as when changed to a different sheet.
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### Testing
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From the command line:
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php test.php path-to-spreadsheet.xls
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In the browser:
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http://path-to-library/test.php?File=/path/to/spreadsheet.xls
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### Notes about library performance
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* CSV and text files are read strictly sequentially so performance should be O(n);
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* When parsing XLS files, all of the file content is read into memory so large XLS files can lead to "out of memory" errors;
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* XLSX files use so called "shared strings" internally to optimize for cases where the same string is repeated multiple times.
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Internally XLSX is an XML text that is parsed sequentially to extract data from it, however, in some cases these shared strings are a problem -
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sometimes Excel may put all, or nearly all of the strings from the spreadsheet in the shared string file (which is a separate XML text), and not necessarily in the same
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order. Worst case scenario is when it is in reverse order - for each string we need to parse the shared string XML from the beginning, if we want to avoid keeping the data in memory.
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To that end, the XLSX parser has a cache for shared strings that is used if the total shared string count is not too high. In case you get out of memory errors, you can
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try adjusting the *SHARED_STRING_CACHE_LIMIT* constant in SpreadsheetReader_XLSX to a lower one.
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### TODOs:
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* ODS date formats;
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### Licensing
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All of the code in this library is licensed under the MIT license as included in the LICENSE file, however, for now the library
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relies on php-excel-reader library for XLS file parsing which is licensed under the PHP license.
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