PHP detects whether the domain name is in the correct format

1. Functions to detect the correctness of the domain name format

Detect domain name format
function Checkurl ($C _url) {
    $str = "/^http (s?): \ /\/(?: [A-za-z0-9-]+\.) +[a-za-z]{2,4} (?: [\/\?#][\/=\?%\ -&~ ' @[\]\ ': +!\.#\w]*)? $/";
    if (!preg_match ($str, $C _url)) {return
        false;
    } else{return
	true;
    }
}

2. How to use

$url = "http://www.baidu.com/"; Fill in the domain name you want to detect
if (! Checkurl ($url)) {
    echo "domain name format is not correct";
} else{
    echo "domain name format is correct";
}