Help with regexp's

[Tekime]

I'm making a basic validation class for a CMS I'm developing. The following function verifies that a username contains nothing but letters, numbers and underscores. How can I extend this regexp to make sure that $value is no less than 5 characters and no more than 20?

    function isUsername($value, $msg) {

    if(eregi("[^a-z0-9_]", $value)) {
		$this->errorlist[] = array("value" => $value, "msg" => $msg);
		return false;
	} else {
		return true;
	}

}

Also, I have considered using a method like they used in this tutorial at DevShed, in which I could pass a validation function the name of a variable, and have it use this internal class function to retreive the value:

    function _getValue($field)
        {
            global ${$field};
            return ${$field};
        }

This way I could fetch the value from within my validation class, and in the case of error I can return the name of the variable it err'd on. This works fine for normal variables, but when it comes to passing an associative array (say $dirtydata["username"]) it cannot retreive the variable name. Is there a way to make this function find return the correct variable name, or is this only possible for a regular variable?

Thanks for any help in advance 🙂

[varasurf]

To make sure that $value is no less than 5 chars and no more than 20 try this.

function isUsername($value, $msg) {

if (strlen($value) < 5 || strlen($value) > 20) {
	return false;
}
else {

    if(eregi("[^a-z0-9_]", $value)) {

        $this->errorlist[] = array("value" => $value, "msg" => $msg);

        return false;

    } else {

        return true;

    }

 }              

}

[Tekime]

Thanks varasurf, although I should have specified that I was hoping for a way to extend the regexp to do the check for me (for the sake of simplicity and speed). If that isn't possible I will most likely use your approach.

[Tekime]

So nobody knows regexps?!?! Don't tell me I have to ask the Perl guys!

j/k, thanks anyway... 😉

[liljim]

if(preg_match("!^[a-z0-9_]{5,20}$!i", $value))
{
  // $value is made up of required letters numbers and underscore
  // and ranges from 5 to 20 characters in length.
}

! = delimiters.
{min,max}
i = modifier (insensitive).
^ start of string (line in multiline mode - negates when inside a character class).
$ end of string (line in multiline mode).

[Tekime]

Thank you liljim, you're the best! I've read the the Perl compatible regexps are quicker than the standard ereg/eregi functions in PHP. Do you know if this is true, and if it's worth using them all the time?

Anyway, thanks again!

[liljim]

Hehe, np.

To answer your question, yes they're faster (can't remember where I've seen some benches, you'll have to have a look around for some) and yes they're worth using over the ereg_ functions, not just for the speed of the replacements / matches, but for the flexibility in syntax. Read up on the pattern syntax and modifiers etc on the manual pages for more info. 🙂