regex to accept a proper url, or none at all

[sid0972]

as the topic says.

 

i ALREADY have the regex to match url, what do i add to accept a NULL as well??

i have tried

 

if(regex to match url)||NULL))
and
iif(regex to match url)||'0'))

 

but they didnt work out, any clue to what do i do?

[Jessica]

If null will evaluate to false.

You need to check if something is equal to null.

[sid0972]

is there a function to check if a value is held by a variable or not?

[requinix]

No, but there is an operator.

if ($variable === null)

...if it's exactly null. If you want to check if a variable is "empty" then

if (empty($variable))

empty() also returns true for "0" but that's not a valid URL so it's okay in this case.

[sid0972]

tried both, didnt work

[Jessica]

How about you post your actual code.

[sid0972]

<?php
function score_valid($score,$link)
{
if (!filled_out($score)) {

     echo "There's something wrong.
    <a href=\"my_oc.php\">Go back and change it.</a>";
     break;
   }

   if (strstr($link, 'http://') === false) {
      $link = 'http://'.$link;
   }
if($link!==NULL)
{

 if (!(@fopen($link, 'r'))) 
  {

 echo "There's something wrong<a href=\"my_oc.php\">Go back and change it.</a>";
 break;
  }
  else { return true; }
}
else { return true; }


}
?>

 

 

function filled_out

 

function filled_out($form_vars) {
 foreach ($form_vars as $key => $value) {
    if ((!isset($key)) || ($value == '')) {
       return false;
    }
 }
 return true;
}

[Christian F.]

Well, beside the obvious absence of any regular expressions, the problem you're having is quite easily spotted.

 

It's because of a flaw in your logic. If you go through the script step-by-step, and keep track of what happens to the contents of the $link variable, you should be able to spot it yourself.

I'll give you a hint: $link always contains a value when you get to the NULL test.

 

Also, your script won't work if the host has turned off fopen_url, which many hosts do. Not only that, but this script is quite open for attacks, which an attacker can utilize to run commands on your server.

You should, at the very least, actually use a RegExp to verify that you've got an URL, before trying to opening the location. I've previously posted a RegExp that validates URLs, and does a fairly good job at it. I recommend using it.

[sid0972]

i think $link wont be NULL cause of this

 

if (strstr($link, 'http://') === false) {
$link = 'http://'.$link;

 

is this what you meant to say?? i have tried without this function included, and failed.

 

also, this might be open for attacks, and thank you for that link, but i didnt understand how it was working.

Care to elaborate?

Edited January 24, 2013 by sid0972

[Christian F.]

Yes, that was exactly what I was thinking about.

 

The RegExp works like any other regular expression. Just copy it, and send it to preg_match () along with your link. It'll return 1 (true) if the string is indeed an URL, or 0 (false) if it's not.

Replace the $link !== null with the preg_match () call, and you should be good.

 

As for how the RegExp itself works, that's a "bit" too complex to explain right off the bat. Suffice to say, it checks all possible (or at least tested) permutations according to the URL RFC.

[sid0972]

thanks for the answer.

Its a bit over my head, but i have stalled this particular thing, i will read pattern matching again.

 

now at least i know whom to catch if i get stuck .

Edited January 24, 2013 by sid0972