what I meant by dont double post is that you created two threads asking the same thing...
and substr() should work here..
Example:
$pass = md5($_POST['password'];
$pass = substr($pass, 10);
you could also do it your way, but you have to realize that when you do str_split it returns an array, each element being 10 characters long.
so you would do:
$passencrypt = md5($_POST["password"]);
$passarray = str_split($passencrypt, 10);
$pass = $passarray[0];