Actionscripting & php

Well I dont know if I post in the correct forum:

I have made a banner.

Frame 1 contents a call to a PHP file hosted in a host service that allows PHP. This PHP file counts the number that this banner is shown and writes this number into a .txt file.

Everyting goes OK if I run the banner from my computer. The PHP file and the .txt file have rights to do the trick. I run the banner from my computer & everything works. But if I upload the banner to a conventional host … It does not work.

can somebody tell me why ?

Thanks in advance.