PHP/cURL function to check a web site status. If HTTP status is not 200 or 302, or the requests takes longer than 10 seconds, the website is unreachable. See https://www.saotn.org/php-curl-check-website-availability/.

check-website-availability.php

<?php
/**
 * PHP/cURL function to check a web site status. If HTTP status is not 200 or 302, or
 * the requests takes longer than 10 seconds, the website is unreachable.
 * 
 * Follow me on Twitter: @HertogJanR
 *
 * @param string $url URL that must be checked
 */
function url_test($url) {
  $timeout = 10;
  $ch = curl_init();
  curl_setopt ($ch, CURLOPT_URL, $url);
  curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt ($ch, CURLOPT_TIMEOUT, $timeout);
  $http_respond = curl_exec($ch);
  $http_respond = trim(strip_tags($http_respond));
  $http_code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
  if (($http_code == "200") || ($http_code == "302")) {
    return true;
  } else {
    // return $http_code;, possible too
    return false;
  }
  curl_close($ch);
}
 
$website = "www.example.com";
if(!url_test($website)) { echo $website ." is down!"; }
else { echo $website ." functions correctly."; }
?>