[RESOLVED] filter out URLs

[Awestruck]

For a full week I have been searching for a code snippet for a very common problem. I was unsuccessful.
Scumbags copy an HTML form using my PHP handler to process the form. They don't do this for kicks, they put dodgy web links in the resulting email in the hope that naive web owners will click them.
There is plenty of advice available for validating entries but absolutely nothing about detecting and blocking URLs.
I use this kind of filtering on my PHP handlers:-
if (empty($username1) || empty($useremail) || empty($useraddrs) || empty($phone)) {
header( "Location: $errorurl" );
exit ;
}
if (!is_numeric($phone)){
header ("Location: $errorphoneurl");
exit ;
}
All I need is to add a code snippet which does this

if (http://is present in ($message)) {
header ("Location: $errormessageurl");
exit ;
}

Would one of you clever chappies devise some code for me as there is nothing out there nor in any manual I have consulted.
Regards Awestruck

[CoderDan]

you can easily get much more elaborate checks, but for your basic one...

if ( stripos( $string, '://' ) !== false )
{
// string probably contains a link as regular text doexn't contain any :// in it, but https://, ftp:// and htp:// etc all do.
}

[Awestruck]

Many thanks CoderDan for your very prompt reply. I will try that and let you know how I get on. Regards, Awestruck

[dagon]

i use

if (substr_count($_POST['comments'], 'http') > 1){

}

so i can allow one link, spammers tend to post dozens, also why not add a CAPTCHA

[Awestruck]

Thank you Dagon, I will try that too.
Regards
Awestruck

[Awestruck]

Hello Coder Dan
I tried your snippet but received a parsing error as follows:-

Call to undefined function: stripos()

It seems that stripos() is a PHP5 only function, does this mean that my host is still using PHP4.5?
My code is
if (stripos ($suggestion, '://') !==false){
header( "Location: $errosuggesturl" );
exit ;
}

I believe that strstr is acceptable to PHP 4.5 and so I could define the function as follows:-
function stripos($haystack, $needle){
return strpos($haystack, stristr( $haystack, $needle ));
}
1. However, as a raw beginner I am not sure how I should define the function to match my bit of code. What would you suggest?

2. Would I also have to surround my bit of code with <?php ... ?> as follows:-
   <?php
   if (stripos ($suggestion, '://') !==false){
   header( "Location: $errosuggesturl" );
   exit ;
   }
   ?>
   Regards
   Awestruck

[CoderDan]

sorry, habit fro me, just use strpos. stripos is php5 version that is case Insensitive, but we're not even searching for alphabet characters so this is irrelevant, i should have used strpos to begin with 😛

[Awestruck]

Many thanks CoderDan

It worked!

Best wishes
Awestruck

[CoderDan]

no worries 🙂