How to access PHP session variables from jQuery function in a .js file?

You can produce the javascript file via PHP. Nothing says a javascript file must have a .js extention. For example in your HTML:

<script src='javascript.php'></script>

Then your script file:

<?php header("Content-type: application/javascript"); ?>

$(function() {
    $( "#progressbar" ).progressbar({
        value: <?php echo $_SESSION['value'] ?>
    });

    // ... more javascript ...

If this particular method isn't an option, you could put an AJAX request in your javascript file, and have the data returned as JSON from the server side script.

I was struggling with the same problem and stumbled upon this page. Another solution I came up with would be this :

In your html, echo the session variable (mine here is $_SESSION['origin']) to any element of your choosing : <p id="sessionOrigin"><?=$_SESSION['origin'];?></p>

In your js, using jQuery you can access it like so : $("#sessionOrigin").text();

EDIT: or even better, put it in a hidden input

<input type="hidden" name="theOrigin" value="<?=$_SESSION['origin'];?>"></input>

If you want to maintain a clearer separation of PHP and JS (it makes syntax highlighting and checking in IDEs easier) then you can create jquery plugins for your code and then pass the $_SESSION['param'] as a variable.

So in page.php:

<script src="my_progress_bar.js"></script>
<script>
$(function () {
    var percent = <?php echo $_SESSION['percent']; ?>;
    $.my_progress_bar(percent);
});
</script>

Then in my_progress_bar.js:

(function ($) {
    $.my_progress_bar = function(percent) {
        $( "#progressbar" ).progressbar({
            value: percent
        });
    };
})(jQuery);