PHP matches URL Regular expression code

PHP Tutorials Match URL Regular expression code
This is a PHP regular expression that gets all the links in the article content
$str = "";

$reg = "<a[ss]*?" (href) s*=s* (? =["']) ((["]) (? <href>[^ "']*) 2) | (? <src>[^s>]+)) [ss]*?> "//The following example is to get the domain name regular expression in the content

Function Get_domain ($url) {
  $pattern =/[w-]+. ( COM|NET|ORG|GOV|CC|BIZ|INFO|CN) (. ( CN|HK)).
  Preg_match ($pattern, $url, $matches);
  if (count ($matches) > 0) {
   return $matches [0];
 }else{
   $rs = Parse _url ($url);
   $main _url = $rs ["Host"];
   if (!strcmp (Long2ip (sprintf ("%u", Ip2long ($main _url)), $main _url)) {
    return $ Main_url;
  }else{
    $arr = Explode (".", $main _url);
    $count =count ($ ARR);
    $endArr = Array ("com", "net", "org", "3322");//com.cn  net.cn
    if ( In_array ($arr [$count-2], $ENDARR) {
     $domain = $arr [$count-3]. "." $arr [$count-2]. $arr [$count-1];
   }else{
     $domain =  $arr [$count-2]. "." $arr [$count-1];
   }
    return $domain;
  }
 }
 
 
 //instance
 
  $STR = "Jfkdlajfdafdjak; Www.jzread.com ";
 echo Get_domain ($str)
 
 //The value is jzread.com