Valid url check in form validation

[eluser]Charles Garrison[/eluser]
[quote author="hugle" date="1257085769"][quote author="Muser" date="1257037344"]I get the following error:

A PHP Error was encountered

Severity: Warning

Message: preg_match() [function.preg-match]: Unknown modifier '|'

Filename: libraries/MY_Form_validation.php

Line Number: 20[/quote]

can you paste exact function/rule?[/quote]

I believe you tried to validate an empty string... You can add this line to the top of the function to check for that:

if( empty($url) ) {
return FALSE;
}