How to validate a domain name using Regex & Php?

Question

I want a solution to validate only domain names not full urls, The following example is what i\'m looking for:

domain.com -> true
domain.net -> true
do         


        

Answer 1

In my case, domain name is considered as valid if the format is stackoverflow.com or xxx.stackoverflow.com

So in addition to other stack answers, I have added checking for www. also.

function isValidDomainName($domain) {
  if (filter_var(gethostbyname($domain), FILTER_VALIDATE_IP)) {
      return (preg_match('/^www./', $domain)) ? FALSE : TRUE;
  }
  return FALSE;
}

you can test the function with this code

    $domain = array("http://www.domain.com","http://www.domain.com/folder" ,"http://domain.com", "www.domain.com", "domain.com/subfolder", "domain.com","sub.domain.com");
    foreach ($domain as $v) {
        echo isValidDomainName($v) ? "{$v} is valid
" : "{$v} is invalid
";
    }