PHP : Human Readable Random String

<?php

    /**************
    *@length - length of random string (must be a multiple of 2)
    **************/
    function readable_random_string($length = 6){
        $conso=array("b","c","d","f","g","h","j","k","l",
        "m","n","p","r","s","t","v","w","x","y","z");
        $vocal=array("a","e","i","o","u");
        $password="";
        srand ((double)microtime()*1000000);
        $max = $length/2;
        for($i=1; $i<=$max; $i++)
        {
        $password.=$conso[rand(0,19)];
        $password.=$vocal[rand(0,4)];
        }
        return $password;
    }
?>