随机生成字符串，数字，手机号，邮箱

/**
 * echo nRand('mail');die;
 * @param array $type
 * @param int $len
 * @return int|string
 */
function nRand($type=[],$len= 20)
{
    $t = gettype($type);
    if($t === 'string'){
        $rand="";
        if($type == 'phone')
        {
            $rand=0;
            for ($i = 1; $i < 9; ++$i) {
                $rand .=mt_rand(0, 9);
            }
            return (int) '13'.$rand;
        }elseif($type === 'mail'){
            $rand=0;
            for ($i = 1; $i < 9; ++$i) {
                $rand .=mt_rand(0, 9);
            }
            return '13'.$rand.'@'.$rand.'com';
        }else{
            for ($i = 0; $i < $len; $i++)
            {
                $rand .= chr(mt_rand(33, 126));
            }
            return  $rand;
        }

    }elseif ($t === "integer"){
        $rand=0;
        $str = '0123456789';
        $max=strlen($str)-1;
        for ($i = 1; $i < $len; ++$i) {
            $rand .=$str[mt_rand(0, $max)];
        }
        return $rand;
    }else{
        $rand = '';
        $str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwsyz0123456789';
        $max=strlen($str)-1;
        for ($i = 1; $i <= $len; ++$i) {
            $rand .=$str[mt_rand(0, $max)];
        }
        return $rand;
    }

}