How to detect the existence of remote files in php

function get_http_response_code($theURL) {
 $headers = get_headers($theURL);
 return substr($headers[0], 9, 3);
}
?>

The function of get_headers is to access a remote address and return the HTTP headers sent by the server in the form of an array. And $header[0] is the status code returned by the server (if nothing else happens, the status code should be the first one returned).

Exclusion example:

/**
 * Fetches all the real headers sent by the server in response to a HTTP request without redirects
 * Gets the headers without redirects
*/
function get_real_headers($url,$format=0,$follow_redirect=0) {
 if (!$follow_redirect) {
 //set new default options
 $opts = array('http' =>
 array('max_redirects'=>1,'ignore_errors'=>1)
);
stream_context_get_default($opts);
}
//get headers
$headers=get_headers($url,$format);
//restore default options
if (isset($opts)) {
 $opts = array(' http' =>
 array('max_redirects'=>20,'ignore_errors'=>0)
);
stream_context_get_default($opts);
}
//return
return $headers;
}
?>