PHP Random Code Generator

function random($size)
{
    $character_set_array = array();
    $character_set_array[] = array('count' => $size, 'characters' => 'ab0cd1ef2gh3ij4kl5mn6op7qr8st9uvwxyz');
    $temp_array = array();
    foreach($character_set_array as $character_set)
    {
        for($i = 0; $i < $character_set['count']; $i++)
        {
            $temp_array[] = $character_set['characters'][rand(0, strlen($character_set['characters'])-1)];
        }
    }
    shuffle( $temp_array );
    return implode('', $temp_array);
}