preg_match assistance needed

Question

Hi I need assistance changing the preg_match to check for 2-16chars A-z 0-9 -_ and space. Right now its checking URL so i'd need to remove the protocol, add space and 2-16 min/max chr.

public function checkUrl($string)
{
    if(empty($string) || preg_match("#^(http|https|ftp)://([A-Z0-9][A-Z0-9_-]*(?:.[A-Z0-9][A-Z0-9_-]*)+):?(d+)?/?#i", $string))
    {
        return true;
    }
    else
    {
        if( isset($this) )
        {
            $this->addError("Input Error");
        }
        return false;
    }
}

Answer 1

I'm not sure what part you want to change, but...

[Need to match] 2-16 chars A-z 0-9 -_ and space.

[\w- ]{2,16}

• \w matches a-z, A-Z, 0-9 and _.
• - will match the literal - in a character class outside of a valid range.
• ' ' will match a space (ignore quotes, Stack Overflow needed them to display). To match any whitespace character, use \s.
• {2,16} will quantify the match to be between 2 and 16 times inclusively.
• You could also change (http|https|ftp) to (?:https?|ftp), which won't capture the group, as you aren't using any back references.

Answer 2

According to regular-expressions.info, there are some things you can do:

• A-Z, a-z, 0-9, and _ can all be matched with \w
• Min/max can be done with brackets {min, max}

So to check for "2-16chars A-z 0-9 -_ and space" we'd have to do something like this:

[- \w]{2,16}