使用mcrypt_encrypt（）快速方法编码数组？

I want to encode a numeric array. After the encode I want to send the data to another server.

$query = "***";
$arr = $wpdb->get_results($query, ARRAY_N);
print_r($arr);

result of print_r:

[0] => Array
    (
        [0] => 3
        [1] => i64lo2
        [2] => Alex
        [3] => ***
        [4] => 213
        [5] => 8
        [6] => 0
        [7] => 1
        [8] => 0
        [9] => 0
        [10] => 1
        [11] => 2015-07-24 12:17:15
        [12] => 2015-07-24 12:17:15
        [13] => ***@***.de
        [14] => 85
        [15] => 1
    )

[1] => Array
    (
        [0] => 7
        [1] => 2tvplb
        [2] => Peter
        [3] => ***
        [4] => 213
        [5] => 8
        [6] => 0
        [7] => 1
        [8] => 0
        [9] => 0
        [10] => 1
        [11] => 2015-07-24 12:18:51
        [12] => 2015-07-24 12:18:51
        [13] => ***@***.de
        [14] => 85
        [15] => 2
    )

my method to encode:

   $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB); 
   $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);   

   for($i = 0; $i <= count($arr); ++$i){
       for($z = 0; $z <= count($arr[$i]); ++$z){
            echo mcrypt_encrypt(MCRYPT_RIJNDAEL_256, "passwort", $arr[$i][$z], MCRYPT_MODE_ECB, $iv);   
$z++;


       }
       $i++;        
    }

But this is so slowly... Have someone a better idea to encode an array? I've to decode the code after the encode.