[SOLVED] relative expressions validation

[Lodius2000]

so i just posted a topic and had it easily solved, so I tested my script and it worked, so i decided to introduce my next big validation line, making sure that the username and or password consists of only letters and or numbers

 

here is what I have

if (! preg_match('/^[a-zA-Z0-9]$/i', $_POST['username'])) {
	$errors[]= "Your username must be <i><b>ONLY</b></i> letters or numbers.";
}

 

that should test the username, which it is doing, but now it will not allow anything that I have tried, I have tried all letters, all numbers, a mix, all caps, whatever, it always returns the error

 

whats wrong

 

Thanks in advance for your help

[sasa]

if (! preg_match('/^[a-zA-Z0-9]+$/i', $_POST['username']))

or

if (preg_match('/[^a-z0-9]/i', $_POST['username'])) 

[Lodius2000]

sasa you are a god, thank you