function is_online( $url ){
	$url = @parse_url($url);
	if (!$url) return false;
	
	$url = array_map('trim', $url);
	$url['port'] = (!isset($url['port'])) ? 80 : (int)$url['port'];
	
	$path = (isset($url['path'])) ? $url['path'] : '/';
	$path .= (isset($url['query'])) ? "?$url[query]" : '';
	
	if (isset($url['host']) && $url['host'] != gethostbyname($url['host'])) {
	
		$fp = fsockopen($url['host'], $url['port'], $errno, $errstr, 30);
	
		if (!$fp) return false; //socket not opened
	
		fputs($fp, "HEAD $path HTTP/1.1
Host: $url[host]

"); //socket opened
		$headers = fread($fp, 4096);
		fclose($fp);
	
		if(preg_match('#^HTTP/.*\s+[(200|301|302)]+\s#i', $headers)){
			//matching header
			return true;
		}
		else return false;
	
	} // if parse url
	else return false;
}

Return true if URL is online.

[PHP] Is URL online?

Online

PHP