How can I use a JavaScript variable as a PHP variable?

Question

I'm trying to include JavaScript variables into PHP code as PHP variables, but I'm having problems doing so. When a button is clicked, the following function is called:

<script type="text/javascript">
    function addTraining(leve, name, date)
    {
        var level_var = document.getElementById(leve);
        var training_name_var = document.getElementById(name);
        var training_date_var = document.getElementById(date);

        <?php
            $result = "INSERT INTO training(level, school_name, training_date) VALUES('level_var', 'training_name_var', 'training_date_var')" or die("Query not possible.");
        ?>

</script>

Is it possible?

Read this about client vs server side: http://stackoverflow.com/questions/2034501/how-does-php-work — Felix Kling, Mar 04 '10 at 12:52

Gordon · Accepted Answer · 2010-03-04T13:00:03.833

PHP is run server-side. JavaScript is run client-side in the browser of the user requesting the page. By the time the JavaScript is executed, there is no access to PHP on the server whatsoever. Please read this article with details about client-side vs server-side coding.

What happens in a nutshell is this:

You click a link in your browser on your computer under your desk
The browser creates an HTTP request and sends it to a server on the Internet
The server checks if he can handle the request
If the request is for a PHP page, the PHP interpreter is started
The PHP interpreter will run all PHP code in the page you requested
The PHP interpreter will NOT run any JS code, because it has no clue about it
The server will send the page assembled by the interpreter back to your browser
Your browser will render the page and show it to you
JavaScript is executed on your computer

In your case, PHP will write the JS code into the page, so it can be executed when the page is rendered in your browser. By that time, the PHP part in your JS snippet does no longer exist. It was executed on the server already. It created a variable $result that contained a SQL query string. You didn't use it, so when the page is send back to your browser, it's gone. Have a look at the sourcecode when the page is rendered in your browser. You will see that there is nothing at the position you put the PHP code.

The only way to do what you are looking to do is either:

do a redirect to a PHP script or
do an AJAX call to a PHP script

with the values you want to be insert into the database.

score 28 · Answer 2 · answered May 01 '12 at 11:50

28

<script type="text/javascript">
var jvalue = 'this is javascript value';

<?php $abc = "<script>document.write(jvalue)</script>"?>   
</script>
<?php echo  'php_'.$abc;?>

answered May 01 '12 at 11:50

dg_0175

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This is wrong on so many levels, and deceptive – CSᵠ Mar 13 '15 at 08:53
4

this is not even an answer – argentum47 Mar 13 '15 at 09:00
4

It is working fine then why is it not an answer @argentum47 – Black Mamba May 09 '17 at 10:41
Hey I need similar type of thing but the problem is that jvalue variable's value is coming through a promise and I get undefined in the $abc. Can someone please help me? – Climb Tree Jan 05 '18 at 13:32
This is a nonsense answer. How can the the PHP running on the server get the output of the `document.write` ? – peeebeee Jun 19 '18 at 07:58
document.write returning undefined. – Ravish Kumar Sharma Dec 28 '19 at 00:34

score 5 · Answer 3 · answered Mar 04 '10 at 12:37

5

You seem to be confusing client-side and server side code. When the button is clicked you need to send (post, get) the variables to the server where the php can be executed. You can either submit the page or use an ajax call to submit just the data. -don

answered Mar 04 '10 at 12:37

Don Dickinson

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score 4 · Answer 4 · answered Mar 04 '10 at 12:38

PHP runs on the server. It outputs some text (usually). This is then parsed by the client.

During and after the parsing on the client, JavaScript runs. At this stage it is too late for the PHP script to do anything.

If you want to get anything back to PHP you need to make a new HTTP request and include the data in it (either in the query string (GET data) or message body (POST data).

You can do this by:

Setting location (GET only)
Submitting a form (with the FormElement.submit() method)
Using the XMLHttpRequest object (the technique commonly known as Ajax). Various libraries do some of the heavy lifting for you here, e.g. YUI or jQuery.

Which ever option you choose, the PHP is essentially the same. Read from $_GET or $_POST, run your database code, then return some data to the client.

score 2 · Answer 5 · edited Apr 11 '11 at 22:10

2

I had the same problem a few weeks ago like yours; but I invented a brilliant solution for exchanging variables between PHP and JavaScript. It worked for me well:

Create a hidden form on a HTML page
Create a Textbox or Textarea in that hidden form
After all of your code written in the script, store the final value of your variable in that textbox
Use $_REQUEST['textbox name'] line in your PHP to gain access to value of your JavaScript variable.

I hope this trick works for you.

edited Apr 11 '11 at 22:10

Peter Mortensen

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answered Jul 11 '10 at 07:28

Sepehr

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Can you please give a working example – Black Mamba May 09 '17 at 10:54
need example code , please – Mahmudul Hasan Sohag Nov 03 '20 at 12:29

score 1 · Answer 6 · edited Mar 13 '15 at 10:14

1

You can take all values like this:

$abc = "<script>document.getElementByID('yourid').value</script>";

edited Mar 13 '15 at 10:14

Hugo Yates

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answered Mar 13 '15 at 09:21

mit

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I used you way and worked. I don't know if its a recommended way though. – user1919 Jan 15 '16 at 15:14
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It doesn't work for me... Is there another way please...? :) – Maryadi Poipo Jun 27 '16 at 17:26

score 0 · Answer 7 · answered Mar 04 '10 at 12:40

0

You can do what you want, but not like that. What you need to do is make an AJAX request from JavaScript back to the server where a separate PHP script can do the database operation.

answered Mar 04 '10 at 12:40

dj_segfault

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How can I use a JavaScript variable as a PHP variable?

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