Question

var strTest = '';

$.post(
    'test.php', 
    { post_test : 1 },
    function(data) {
        strTest = data.split('a');

        $.post(
            'test_2.php', 
            { post_test_2 : 2 },
            function(sData) {
                alert(strTest);
            }
        );
    }
);

strTest – is empty! Why?

Answer 1

Your code seems to be working. I have reproduced your case in a jsfiddle and as you can see from the resulting alert, strTest contains data. The problem probably stems from the fact that test.php returns nothing.