PHP random word function

randomWord.php

<?php
function generateRandomWord($length=10, $level=2){
    list($usec, $sec) = explode(' ', microtime());
    srand((float) $sec + ((float) $usec * 100000));
		
    $validchars[1] = "0123456789abcdfghjkmnpqrstvwxyz";
    $validchars[2] = "0123456789abcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $validchars[3] = "0123456789_!@#$%&*()-=+/abcdfghjkmnpqrstvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_!@#$%&*()-=+/";

    $word  = "";
    $counter   = 0;
		
    while ($counter < $length) {
        $actChar = substr($validchars[$level], rand(0, strlen($validchars[$level])-1), 1);
			
        // All character must be different
        if (!strstr($word, $actChar)) {
            $word .= $actChar;
            $counter++;
        }
    }
		
    return $word;
}