PHP regular method to determine whether a string is a domain name

Usually matching the format requirements of domain names:

Regular rules for matching domain names:

Let’s see an example,

<?php
$url = 'www.test.com';
$search = '/---正则N---/';
if(preg_match($search,$url)){
 echo '匹配';
}else {
 echo '不匹配';
} //edit by bbs.it-home.org
?>

The following regular expressions are all sourced from the Internet for your reference.

Regular 1 b([a-z0-9]+(-[a-z0-9]+)*.)+[a-z]{2,}b Bad match: length>60 Rule 2 ^(([^-][a-z0-9A-Z-_]+.)*)[^-][a-z0-9A-Z-_]+(.[a-zA-Z]{2 ,4}){1,2}$ Bad match: length>60 Bad match: www.te_st.com Rule 3 (([wd-_]+.):?[^-_])+w{2,4} Not matching: test.com.cn Bad match: www.te_st.com Rule 4 [a-zA-Z0-9][-a-zA-Z0-9]{0,62}(.[a-zA-Z0-9][-a-zA-Z0-9]{0,62} )+.? No errors yet Rule 5 (?