Modifying PHP Session Variables with JavaScript

Question

I have some implicit PHP functions which are to be called on particular front-end events; such as button onclicks. By doing so this should modify my PHP SESSION variable accordingly. However, both functions, setAlan() and setMark(), seem to be getting called even if I just want the first one to execute.

<?php
    session_start();

    function setAlan() {
        $_SESSION['passed_user']='alan';
    }
    function setMark() {
        $_SESSION['passed_user']='mark';
    }
?>

<script>
    function getAlan() { $(document.body).append('<?php setAlan(); ?>'); }
    function getMark() { $(document.body).append('<?php setMark(); ?>'); }
    function show() { alert(' <?php echo "{$_SESSION['passed_user']}" ?> '); }
</script>

<div class="pod">
    <div class="pod_title"><h2>Select a User</h2></div>
    <div>
        <input type="button" onclick="getAlan();" value="alan">
        <input type="button" onclick="getMark();" value="mark">
        <input type="button" onclick="show();" value="show">
    </div>
</div>

I don't understand why setMark() is being called automatically? By what I've written, I believe I am only defining the PHP functions, not calling them; I use JS for that. Am I missing something? Thanks in advance!

PHP is executed server side. Appending PHP on the client side will not work. U'll have to use ajax for this to work. — DarkBee
– DarkBee, Commented Jul 22, 2014 at 8:48
@DarkBee Umm, it is working, i believe. I just want to implement a conditional based on each of the buttons... Any solution for this? — Jim22150
– Jim22150, Commented Jul 22, 2014 at 8:50
U think its working because PHP is parsed BEFORE any output is sent to the user. If u check your source code u will see that function getAlan() appends an empty string to the source because the PHP in it is already parsed and executed thus making the session having a value of mark — DarkBee
– DarkBee, Commented Jul 22, 2014 at 8:55

Pierre · Accepted Answer · 2014-07-22 09:05:18Z

1

PHP is executed first, server side. Once PHP is done, your browser ( client ) gets the result, Javascript is executed on the client, so after PHP is done.

You can't mix javascript and PHP as you did with:

<script>
  function getAlan() { $(document.body).append('<?php setAlan(); ?>'); }
  function getMark() { $(document.body).append('<?php setMark(); ?>'); }
  function show() { alert(' <?php echo "{$_SESSION['passed_user']}" ?> '); }
</script>

However you can use Javascript to call some server side PHP script with ajax ( Asynchronous JavaScript and XML ).

http://www.w3schools.com/ajax/default.ASP

answered Jul 22, 2014 at 9:05

Pierre

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