Does not equal?

is there a symbol for Does Not Equal? i am making a registration script and i need to have it so that if $password1 doesnt equal $password2, then it outputs and error message.

if($a!=$b)

For future reference, it would be advisable to get into the habit of checking the PHP manual (http://www.php.net/manual/en/).

For example, here are all the operators (http://www.php.net/manual/en/language.operators.php).