String Expression for apha numeric password

I need a string expression to verify an alpha numeric password. This is what
i've come up with , however it does not work:

PHP Code:

---

elseif ( (!ereg ("^[a-zA-Z]+$", $password)) || (!ereg ("^[0-9]+$",
$password))) 


---

can anybody help? Thanks in advance
ADAM

try this

elseif ( (!ereg ("^[:ALPHA:]+$", $password)))

or

elseif ( (!ereg ("^[a-zA-Z0-9]+$", $password)))