PHP生成指定长度随机数最简洁的方法

function generate_code($length = 4) {
    return rand(pow(10,($length-1)), pow(10,$length)-1);
}

function generate_code($length = 4) {
    $min = pow(10 , ($length - 1));
    $max = pow(10, $length) - 1;
    return rand($min, $max);
}