Did you understand this part ?
Before being able to provide you support, we need to know as much as possible about what your are trying to achieve, and how your are going about it. We don't know if it is an AI2 issue because there are so many external variables that come into play. From what you have said:
You are using the web component with the POST (file?) block ?
You are posting files (?) but we don't know what type of files ?
You are posting to an online server which is running a "php program", but we don't know how the php program works, how the server is setup or what is being used to store the file once it arrives at the server ? Is it your own server ? LAMP/WAMP/Other ? php/mySQL or just php ?
Have you been through the server configuration to check for settings that might be causing this ?
Can you upload any file through other means, curl etc ?
Help us to help you.....