How to use cookies to store multidimensional arrays in PHP

//Save
$arr = array(1,2,3);
$arr_str = serialize($arr);
setcookie("a",$arr_str);

//Take out
$ arr_str = $_COOKIE['a'];
$arr = unserialize($arr_str);

Method 2: Set a multi-key value cookie, please note that the key value must be given

$arr = array(1,2,3);
setcookie("a[0]", $arr[0]);
setcookie("a[1]", $arr[1] );
setcookie("a[2]", $arr[2]);

Note: The above method is copied from elsewhere. I tried the first method and it was successful. It is also more convenient. I have not tried the second method, so please test it more.