PHP正则表达式允许在字符之间使用“a-z”和“1-9”和“ - ”以及最小的一个或最多两个“。”

Question

I need a PHP RegEx that allow "a-z" & "A-Z" & "-" & "."

• "." is allow to use minimum 1 and maximum 2 times and not together ".."
• "-" may use many times but not together "--" and cannot use after last dot "."

in other words I want to validate domain or sub-domain name like:

my-domain.com or sub.my-domain.com

and for eg: my--domain.com or my-domain.com-net or my-domain-.com or etc must return false.

if (!preg_match('/^[a-zA-Z0-9][a-zA-Z0-9-]{1,61}[a-zA-Z0-9]\.[a-zA-Z]{2,}$/', $odomain)) {
    //do something
}

Answer 1

If you are sure domains and TLDs do not contain Unicode characters you may want to try:

(?i)^[a-z\d]+([.-][a-z\d]+)*\.[a-z]+$

This matches user.sub.domain.com too (disregarding first rule which I didn't consider valid)

Live demo

PHP code:

preg_match('/^[a-z\d]+([.-][a-z\d]+)*\.[a-z]+$/i', $domain);