What are the quick and reliable ways to check the availability of a site in PHP?

Question

PHP

It is required to check the site by url whether it is available now or not.
Now I'm using this script:

function accessSite($url) {
  if (preg_match('/[^0-9a-z-_A-Z:\.]/is', $url)!=0) {
    include("modules/idna_convert.class.php");
    $IDN=new idna_convert(array('idn_version' => '2008'));
    $url=$IDN->encode($url);
  }
  @$status=get_headers($url);
  if ($status) {
    if (in_array("HTTP/1.1 200 OK", $status) || in_array("HTTP/1.0 200 OK", $status)) return true;
  }
  return false;
}

But sometimes it happens that it takes a very long time to check the availability and several times the script gave the wrong result.
ps idna_convert.class.php - conversion of Russian domains.

Answer 1

It is necessary to determine the accessibility criteria:
1) exceeding the connection timeout;
2) getting some expected response via http.
The request can be made via curl and set a timeout in it.

Answer 2

The simplest is to get the 200th header from the site.
You can also check the dns record using checkdnsrr()