PHP sockets

As i search through the list of books i need to read, i figured i would ask something here as well.

To my knowledge software on a web site written as a script (C++, PHP, Perl, etc...) could only be executed when a user sends a request to it. Meaning it's not running constantly, instead performs the task as hand each time a request is sent to it. Because it uses HTTP, it's connectionless. Each execution of the script is a different connection. One doesnt know anything about the other (unless session management is used). Follow me so far?

Then i came across articles on socket programming with PHP. The way these scripts were set up, they opened up port xxx and waited for a connection. I didnt think this was possible. THe program written in PHP was accepting a connection and sending data back and forth like it was 1 continuous session instead of multiple sessions(like normal scripts are).

I assume if this was done in PHP then the same could be done in CGI with C++ or Perl. THis would mean that a web based application could act as any other complex application handling users and creating a network.


Am i missing something? any help/comments are appreciated.
The only book i have on PHP/SQL did not talk about this at all.

The socket functions are mainly used to communicate between servers. You might use it to for approval script or something similar. You could theortically use them to handle server client relationships but there are better tools available to do this.

Like what?