Script to check if recip link form field is set correctly

Need to check if 2 form fields contains the same domain in url

[silverbytes]

I receive lot of garbage in my php form for reciprocal link exchange. Specifically I get some form emails where user fills the form where he mention where he'd like to get a link (their real website) and other field where he must put where in his website is linking to me.

Many of them just put a bogus domain in reciprocal field, (they simulate being linking to me but that domain is not the same where they want a link back)

I need a script that detects that, BEFORE they submit, and STOP the submission if that is incorrect.

IE: Correct form

url: [thewebsitewheretheywantalinkfrom.me...]
reciprocal_url:

[thewebsitewheretheywantalinkfrom.me...]

IE: Incorrect and must be stopped:
url: [thewebsitewheretheywantalinkfrom.me...]
reciprocal_url: [abogusurl...]

May you suggest some php lines to add to my form?

[superpower]

I would just validate it as part of the submit form.

If it's not the right form of url you have a couple options:

1. Have your script fix the mistake. ie. if there are two http's as in your example, you can just use something like str_replace (this is a php example) or preg_replace to get rid of erroneous extra stuff like that. Google for a link validation regular expression.

2. Send back an error without further processing if it;s the wrong form of url. You would also need regex for this vlaidation.

Learn/search for regex stuff. Have fun :)

[coopster]

In addition to the regular expression matching for a valid url you could then use fsockopen() [php.net] to send a HEAD request to check for a valid url.

[silverbytes]

I have no idea of how to do that (sorry I'm not programmer) can you paste an example of what you're saying?

[coopster]

RFC2616 states ...

9.4 HEAD

   The HEAD method is identical to GET except that the server MUST NOT 
   return a message-body in the response. The metainformation contained 
   in the HTTP headers in response to a HEAD request SHOULD be identical 
   to the information sent in response to a GET request. This method can 
   be used for obtaining metainformation about the entity implied by the 
   request without transferring the entity-body itself. This method is 
   often used for testing hypertext links for validity, accessibility, 
   and recent modification.

... which seems to lend itself nicely for the problem you are addressing. So what you need to do is open a socket to the intended target and issue a HEAD request. Then read the response for a positive status.

Here is a quick example to get you started ...

<pre> 
<?php 
$target = 'www.example.com'; 
$page  = '/path/to/page.htm'; 
$fp = fsockopen($target, 80, $errno, $errstr, 30); 
if (!$fp) { 
 echo "$errstr ($errno)"; 
} else { 
 $out = "HEAD $page HTTP/1.1\r\n"; 
 $out .= "Host: $target\r\n"; 
 $out .= "Connection: close\r\n\r\n"; 
 fwrite($fp, $out); 
 $response = ''; 
 while (!feof($fp)) { 
  $response .= fgets($fp); 
 } 
 fclose($fp); 
 print $response; 
 if (preg_match("/200 OK/", $response)) { 
  print 'good target'; 
 } else { 
  print 'bad target'; 
 } 
} 
</pre> 
>?

I left the printed response headers so you can see how they look coming back.