How to catch curl errors in PHP

If CURLOPT_FAILONERROR is false, http errors will not trigger curl errors.

<?php
if (@$_GET['curl']=="yes") {
  header('HTTP/1.1 503 Service Temporarily Unavailable');
} else {
  $ch=curl_init($url = "http://".$_SERVER['SERVER_NAME'].$_SERVER['PHP_SELF']."?curl=yes");
  curl_setopt($ch, CURLOPT_FAILONERROR, true);
  $response=curl_exec($ch);
  $http_status = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  $curl_errno= curl_errno($ch);
  if ($http_status==503)
    echo "HTTP Status == 503 <br/>";
  echo "Curl Errno returned $curl_errno <br/>";
}

You can use the curl_error() function to detect if there was some error. For example:

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $your_url);
curl_setopt($ch, CURLOPT_FAILONERROR, true); // Required for HTTP error codes to be reported via our call to curl_error($ch)
//...
curl_exec($ch);
if (curl_errno($ch)) {
    $error_msg = curl_error($ch);
}
curl_close($ch);

if (isset($error_msg)) {
    // TODO - Handle cURL error accordingly
}

See the description of libcurl error codes here

See the description of PHP curl_errno() function here

See the description of PHP curl_error() function here