How can I check if a URL exists via PHP?

Question

How do I check if a URL exists (not 404) in PHP?

Answer 1

I run some tests to see if links on my site are valid - alerts me to when third parties change their links. I was having an issue with a site that had a poorly configured certificate that meant that php's get_headers didn't work.

SO, I read that curl was faster and decided to give that a go. then i had an issue with linkedin which gave me a 999 error, which turned out to be a user agent issue.

I didn't care if the certificate was not valid for this test, and i didn't care if the response was a re-direct.

Then I figured use get_headers anyway if curl was failing....

Give it a go....

/**
 * returns true/false if the $url is present.
 *
 * @param string $url assumes this is a valid url.
 *
 * @return bool
 */
private function url_exists (string $url): bool
{
  $ch = curl_init($url);
  curl_setopt($ch, CURLOPT_URL, $url);
  curl_setopt($ch, CURLOPT_NOBODY, TRUE);             // this does a head request to make it faster.
  curl_setopt($ch, CURLOPT_HEADER, TRUE);             // just the headers
  curl_setopt($ch, CURLOPT_SSL_VERIFYSTATUS, FALSE);  // turn off that pesky ssl stuff - some sys admins can't get it right.
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
  // set a real user agent to stop linkedin getting upset.
  curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36');
  curl_exec($ch);
  $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  if (($http_code >= HTTP_OK && $http_code < HTTP_BAD_REQUEST) || $http_code === 999)
  {
    curl_close($ch);
    return TRUE;
  }
  $error = curl_error($ch); // used for debugging.
  curl_close($ch);
  // just try the get_headers - it might work!
  stream_context_set_default(array('http' => array('method' => 'HEAD')));
  $file_headers = @get_headers($url);
  if ($file_headers)
  {
    $response_code = substr($file_headers[0], 9, 3);
    return $response_code >= 200 && $response_code < 400;
  }
  return FALSE;
}