Simple Username Creation Validation with PHP

Discussion

1. Иван

   I like the approach — instead of matching a word boundary e.g. ^[a-zA-z0-9]*$ you match the first invalid character. I wonder what the speed difference is…

   BTW, you can use [^\w\d] insead ;) It’s lazier
2. Иван

   My bad. You cant use \w since it matches _ as well. On the other hand \w handles \d, so if you are looking for something quick for chars, digits and _ — you can use \w.
3. Brian

   You could also use PHP’s ctype_alnum to match only alphanumeric characters
   which matches (ever so slightly) faster than its equivalent regular expression,
   and still retain future flexibility by using something like:

   function username($input, $pattern = false)
   {
          return ($pattern) ? !ereg($pattern, $input) : ctype_alnum($input);
   }
   

   Of course the speed difference is on the order of nanoseconds,
   but it is faster nonetheless.
4. Jeff Hartman

   A better method name would be useful. ;)
5. david

   @Jeff: Ooops. I have this function within a class. I actually use it like this:

   if($valid->username($input)) {
     // move on...
   }
   

   I simply didn’t rename it for the blog. I’ll do that quick!
6. Rexxars

   A word of warning, ereg is being removed in PHP6 because of the more powerful and usually faster preg. Altering your code to work with pregs is easy and safer should the server you’re on upgrade to PHP6 sometime in the future:

   function validate_username($input, $pattern = '/[^A-Za-z0-9]/')
   {
       return !preg_match($pattern, $input);
   }
   
7. Dmytri Kleiner

   ereg will be deprecated in php 5.3 and removed in 6, use preg instead
8. Sushant Danekar

   ereg is not available in php 5.3.0

   any alternative for this ?
9. Nolan Hawkins

   I’m rather new to regexp, and am just trying to get something exactly like this to work, but it just isn’t. I got annoyed, and then simplified as much as possible to this:
   

   
   and it isn’t responding anything except 0, no matter what I try.
10. Nolan Hawkins

    Oops sorry. Anyways, it’s just a text input that posts to itself, and it deals with the post by doing

     if(!is_null($_POST["f"])){
    $input=$_POST["f"];
    $pattern = '[^A-Za-z0-9]';
    $a=preg_match($pattern,$input);
    echo $a;
    }
11. ifreelancer.asia

    The Best way I recommend is this :-

        $str = "";
        function validate_username($str) 
        {
            $allowed = array(".", "-", "_"); // you can add here more value, you want to allow.
            if(ctype_alnum(str_replace($allowed, '', $str ))) {
                return $str;
            } else {
                $str = "Invalid Username";
                return $str;
            }
        }