Javascript echos PHP command, not PHP variable

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?

whether the script file is parsed by the server... or is it a static file — Arun P Johny, Nov 26 '13 at 03:07
it looks like the script file is a static file so the php commands are not processed and just sent as it is.... so in attempt2 you have an invalid javascript syntax — Arun P Johny, Nov 26 '13 at 03:09
@SubodhGhulaxe $logged_in is either a 1 or a 0 (in this case, a 1) — cssyphus, Nov 26 '13 at 03:20
@ArunPJohny The js/jQuery is in an external file included via `` tags. Is that what you mean? — cssyphus, Nov 26 '13 at 03:21
yes..... that is the reason... what you need to do is to move the variable `logged_in` to a PHP file as a global variable then use it in the function — Arun P Johny, Nov 26 '13 at 03:23
ick... global variables. But yes, he's right. Don't use a general global though, do it right and store this inside a superglobal... look into using `$_SESSION` and `$_COOKIE` — Brian Vanderbusch, Nov 26 '13 at 03:25
Arrrgh... Now I'm getting `` inside the alert box. I am losing confidence in the awesomeness of my skillz. — cssyphus, Nov 26 '13 at 03:31
confidence must be maintained at all costs! tell you what, throw us a link to a **[Github](https://github.com/)** repo for this, and I'll fork and issue a pull request to help you with your code. — Brian Vanderbusch, Nov 26 '13 at 05:30

Joe T · Accepted Answer · 2013-11-26T03:12:53.550

0

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.

edited Nov 26 '13 at 03:12

answered Nov 26 '13 at 03:05

Joe T

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Yes, php runs first, but as far as the interpreter is concerned, the javascript he wrote is markup, so it would go ahead and process the php inside that markup. As long as his `$logged_in` var value is present on the server, the javascript should run as intended. It's more likely an issue of formatting... or he's not running that file as a php file. – Brian Vanderbusch Nov 26 '13 at 03:12
Thanks for the great explanation. Before I re-code using ajax, I have one question: if the php has set a variable at page load (and the value/variable has already been set), then why is that PHP variable not accessible at any point? – cssyphus Nov 26 '13 at 03:16
@BrianVanderbusch You've said what I thought myself. The $logged_in var *is* present on the server, and the file is a .php file (and all the other PHP things inside it work). However, the js is in an external file included via ` – cssyphus Nov 26 '13 at 03:18
1

if you have *any* server side code or tags on your page, that page has to be saved as a server side page, in this case being .php. If your index.js file is the file with the code above... then yes, that is absolutely the problem. – Brian Vanderbusch Nov 26 '13 at 03:22

score 0 · Answer 2 · edited May 23 '17 at 11:59

Explanation of Solution:

The question was caused by a misunderstanding of the relationship between PHP and javascript.

Once the page has rendered (that is, inside jQuery's $(document).ready()), all PHP regular variables no longer exist. The PHP super-variables exist (such as $_SESSION, but not $logged_in.

To possible solutions:

Store logged-in value in a super-global: e.g. $_SESSION['logged-in'], or
Use AJAX inside the javascript $(document).ready() to query PHP if the user is logged in, and receive the answer in the AJAX function's success: function.

Simple explanation of AJAX and how it works

Javascript echos PHP command, not PHP variable

2 Answers2