Martynas Jusevicius has pointed out a handy tool to work with Microsoft Excel files in PHP - PHPExcelReader.

There is a nice tool for reading Microsoft Excel files called PHPExcelReader. It works with .xls files up to Excel version 2003, which are based on the BIFF format (later versions use OOXML). It is written in native PHP and does not require any third-party libraries or the MS Office package.

He includes an example of it in use - a loop that runs through the cells of a spreadsheet and outputs each of them (going across the row via an inner for loop as well).