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Relational databases that speak SQL are the data-storage backbone for most developers. Unfortunately, but most of the data that's created outside the control of the technology caste at a typical workplace is in Excel format. Because of this, being able to procedurally read and write Excel documents with a familiar language can open up a whole world of possibilities for automation and data migration.

Assuming you're attempting to read and write standard text (Ie. not binary/graphic) data from Excel worksheets, this is actually fairly doable in PHP and Perl.

A recent article by Mike Diehl at Linux Journal peaked my interest in this. He shows off some of the features of the Spreadsheet::ParseExcel Perl module, which can be used to pull data and even formatting information from cells in an Excel worksheet. Once you have your hands on the data, you can do what you want with it: output it to XML, toss it in a database for subsequent querying, or even convert it into other Excel documents (oh, the shame).

Perl Excel Libraries and Information
Spreadsheet:ParseExcel - Read from Excel 95/97/2000 documents
Spreadsheet:WriteExcel - Write to Excel 97/2000/2002/2003 documents
Linux Journal - Reading Native Excel Files in Perl

There are libraries for dealing with native Excel files in PHP as well. The following two seem to be the only options for binary Excel documents.

PHP Excel Libraries
PHP Excel_Reader - Read Excel 95 and 97 documents
Spreadsheet_Excel_Writer - Write Excel 5.0 documents
Reading and Writing Spreadsheets with PHP

With the most recent version of Excel, there is an XML file format option that will allow you to read and write data in a worksheet by directly interacting with the saved file's DOM. IBM has a document that details doing this with PHP, and it would be straightforward to apply this technique to Perl as well.

Read/Write XML Excel Data in PHP

Finally, if all you need to do is output a document that can be read in Excel, a standard CSV-format file will usually do the trick. Escaping can be a bit tricky, however, and my preferred format has become a plain-old HTML table. Just create a file that contains a TABLE element (no BODY or HTML tags necessary), with any number of TR rows and html-escaped data in the TDs, and save it out. If you use the XLS file extension, it will open directly in Excel with a double-click and Excel never seems to mind reading in the data.

Do you have any other Excel programming hacks? Give us a shout in the comments.