How basic syntax adds elements to the session array

Ask a very weak basic grammar.
If it is an ordinary array, we can do this:

$arr =array (); $arr []= "1"; $arr []= "2";p Rint_r ($arr);//This enables the purpose of adding elements to the $arr array

The problem is, if I define a session array:

$_session[' a ']=array ();//I want to add 1, 22 elements to an array of $_session[' a '], what should I say?

Reply to discussion (solution)

$a =array ("a", "B"); $_session["a"]= $a;  Print_r ($_session["a"]);

What's the difference?

$_session[' a ' [] = 1;$_session[' a ' [] = 2;

$_session[' a ']=array (); $_session[' a ' [] = 1;$_session[' a ' [] = 2;

$_session[' A '][]=1;$_session[' a '][]=2;

You're a two-dimensional array, and you're going to append the brackets in the back.

$_session[' a '][]= "xxx"

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