Javascript echos PHP命令，而不是PHP变量

Question

The jquery code:

$('.up_IMG').click(function() {
    if (notLoggedIn()) return false;
    alert('Got to here');
});

The function (attempt #1): in quotes:

function notLoggedIn() {
    alert('here');
    logged_in = "<?php echo json_encode($logged_in); ?>";
    alert('Logged in: ' + logged_in);
}

OR json_encoded (attempt #2):

function notLoggedIn() {
    alert('here');
    logged_in = <?php echo json_encode($logged_in); ?>;
    alert('Logged in: ' + logged_in);
}

When attempt #1 fn is called, the first code block's alert displays:

The second code block does nothing.

The PHP variable does exist and has the value zero.

Any thoughts as to what's happening?

Answer 1

If you're calling this code with a 'click', at that point it's too late for PHP to help you asynchronously.
PHP runs when the page is loaded, not after. It's a matter of timing. PHP can never output something that doesn't exist yet, so it will always be blank.