No replies to this topic

[Shoel]

A fairly common thing people come across is the need to check whether a URL for an external file/resource, such as an XML document hosted by a 3rd party, is valid. I've seen various complicated ways of doing this, but the method I've found the quickest and easiest for simply checking whether it exists or not - is the following:

(This is intended for PHP 5)

<?php
/**
 * Check if an external URL is valid
 *
 * @param string $path
 * @return boolean
 */
function check_path($path){
  
  $headers = @get_headers($path);
  
  if (preg_match("/200/", $headers[0])){
    return true;
  }
  return false;
}
?>

In a nutshell it tries to fetch the HTTP headers for the given path/URL from the webserver hosting it, and if the response code is "200" (also known as "OK") - which indicate that the request has been received, understood, accepted and processed successfully. (The @ in front of the function call is PHP's error control operator - which tells it to ignore any errors/warnings it might generate.)

The same method can also be used to check content size (in bytes):

<?php
$headers = @get_headers($path, 1);

return $headers['Content-Length'];
?>

The second parameter to get_headers() simply tells it to parse the result and set the array key's to the corresponding header field names instead of numerical keys - which is a more reliable way of doing it. Note that even with this, the HTTP response code will always be key 0 in the array - for the sake of consistency. Thus we do not need to concern ourselves with the keys in the initial function described above.