Sir,
I have a working barcode generator already made, and it's web based, but built in Java instead of PHP. I coded it as a part of a project i worked on a few years ago. The project never saw the light because of unreparable disaccord between the two partners of the firm, but i still have the source code. It would need only some minor changes to adapt it in order to read the barcode strings from a file (in the original form, it was inputed manually via a text field).
The excel file should be exported in formatted text format before being fed into the barcode generator.