How to see if a variable contains a word.

[MichaelHe]

I have a message written in a form field, and this message must not contain urls.

So how do I find out if it contains an url or not.
something like

IF ($message -some sign for containing-  'www') {$something='error';}

Or how do I do it ?

[thorpe]

Check out the manual entry for [man]strpos/man.