How can I store JavaScript variable output into a PHP variable

Question

I have the following code in JavaScript    lt script gt  var a  Hello    lt  script gt    PHP Code -   lt  php   variable      I want the above JavaScript variable  a  value to be stored here   gt    Note   I don t want it in a form submission  I have some logic in JavaScript and I want to use it in the same PHP page    Please let me know how I can do this

User · Accepted Answer

You have to remember that if JS and PHP live in the same document, the PHP will be executed first (at the server) and the JS will be executed second (at the browser)--and the two will NEVER interact (excepting where you output JS with PHP, which is not really an interaction between the two engines).

With that in mind, the closest you could come is to use a PHP variable in your JS:

<?php
$a = 'foo'; // $a now holds PHP string foo
?>
<script>
    var a = '<?php echo $a; ?>'; //outputting string foo in context of JS
                                 //must wrap in quotes so that it is still string foo when JS does execute
                                 //when this DOES execute in the browser, PHP will have already completed all processing and exited
</script>
<?php
//do something else with $a
//JS still hasn't executed at this point
?>

As I stated, in this scenario the PHP (ALL of it) executes FIRST at the server, causing:

a PHP variable $a to be created as string 'foo'
the value of $a to be outputted in context of some JavaScript (which is not currently executing)
more done with PHP's $a
all output, including the JS with the var assignment, is sent to the browser.

As written, this results in the following being sent to the browser for execution (I removed the JS comments for clarity):

<script>
    var a = 'foo';
</script>

Then, and only then, will the JS start executing with its own variable a set to "foo" (at which point PHP is out of the picture).

In other words, if the two live in the same document and no extra interaction with the server is performed, JS can NOT cause any effect in PHP. Furthermore, PHP is limited in its effect on JS to the simple ability to output some JS or something in context of JS.

User · Answer

JavaScript variable   PHP variable try follow -   lt script gt  var a  Hello    lt  php  variable  a     gt   lt  script gt    Note -It run only when you do php code under script tag I have a successfully initialise php variable

User · Answer

If this is related to a form submission  use a hidden inputinside the form and change the hidden input value to this variable value  Then you can get that hidden input value in the php page and assign it to your php variable after form submission   Update   According to your edit  it seems you don t understand how javascript and php works  Javascript is a client side language  and php is a serverside language  Therefore you cannot execute javascript logic and use that variable value to a php variable when you execute relevant page in the server  You can run the relevant javascript logic after client browser process the web page returned from the web server  which has already executed the php code for the relevant page   After the execution of the javascript code and after assigning the relevant value to the relevant javascript variable  you can use form submission or ajax to send that javascript variable value to use by another php page  or a request to process and get the same php page

User · Answer

You can solve this problem by using AJAX  You don t need to load JQuery for AJAX but it has a better error and success handling than native JS   I would do it like so   1  add an click eventlistener to all my anchors on the page  2  on click  you can setup an ajax-request to your php  in the POST-DATA you set the anchor id or the text-value 3  the php gets the value and you can setup a request to your database  Then you return the value which you need and echo it to the ajax-request  4  your success function of the ajax-request is doing some stuff  For more information about ajax-requests look back here   -  Ajax-Request NATIVE https   blog garstasio com you-dont-need-jquery ajax   A simple JQuery examle      button   click function        ajax  url   demo test txt   success  function result           div1   html result

User · Answer

The ideal method would be to pass it with an AJAX call  but for a quick and dirty method  all you d have to do is reload the page with this variable in a   GET parameter -    lt script gt    var a  Hello     window location href   window location href   a   a   lt  script gt    Your page will reload and now in your PHP  you ll have access to the   GET  a   variable    lt  php     variable     GET  a      gt

User · Answer

in your view     lt  php  value     lt p id  quot course id quot  gt  lt  p gt     gt   javascript code    var course   document getElementById  quot courses quot   value      document getElementById  quot course id quot   innerHTML   course

User · Answer

lt html gt    lt head gt       lt script gt          var a  Hello        lt  script gt    lt  head gt     lt body gt        lt  php          echo  variable     lt script gt document write a  lt  script gt      I want above javascript variable  a  value to be store here       gt   lt  body gt

User · Answer

You really can t  PHP is generated at the server then sent to the browser  where JS starts to do it s stuff  So  whatever happens in JS on a page  PHP doesn t know because it s already done it s stuff   manjula is correct  that if you want that to happen  you d have to use a POST  or an ajax

[php] How can I store JavaScript variable output into a PHP variable?

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