How to Put JavaScript Variable in PHP Echo

How can I store JavaScript variable output into a PHP variable?

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:

$a = 'foo'; // $a now holds PHP string foo
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
//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:

  1. a PHP variable $a to be created as string 'foo'
  2. the value of $a to be outputted in context of some JavaScript (which is not currently executing)
  3. more done with PHP's $a
  4. 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):

var a = 'foo';

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.

How do I pass JavaScript variables to PHP?

You cannot pass variable values from the current page JavaScript code to the current page PHP code... PHP code runs at the server side, and it doesn't know anything about what is going on on the client side.

You need to pass variables to PHP code from the HTML form using another mechanism, such as submitting the form using the GET or POST methods.

<DOCTYPE html>
<title>My Test Form</title>

<form method="POST">
<p>Please, choose the salary id to proceed result:</p>
<label for="salarieids">SalarieID:</label>
$query = "SELECT * FROM salarie";
$result = mysql_query($query);
if ($result) :
<select id="salarieids" name="salarieid">
while ($row = mysql_fetch_assoc($result)) {
echo '<option value="', $row['salaried'], '">', $row['salaried'], '</option>'; //between <option></option> tags you can output something more human-friendly (like $row['name'], if table "salaried" have one)
<?php endif ?>
<input type="submit" value="Sumbit my choice"/>

<?php if isset($_POST['salaried']) : ?>
$query = "SELECT * FROM salarie WHERE salarieid = " . $_POST['salarieid'];
$result = mysql_query($query);
if ($result) :
while ($row = mysql_fetch_assoc($result)) {
echo '<tr>';
echo '<td>', $row['salaried'], '</td><td>', $row['bla-bla-bla'], '</td>' ...; // and others
echo '</tr>';
<?php endif?>
<?php endif ?>

How to echo a JS variable to php?

You can not pass the JavaScript variable up to PHP to index the $list array. What you can do is to pass the whole array down to JavaScript as JSON encoded and then index into that.

See: Convert php array to Javascript

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

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.

Use javascript variable in php code

You can't use javascript variable in php code. Php code run's on the serverside and javascript code runs in the client side. You can't ask the browser to run php code.

Your variable loc will have a value only when the code reaches the browser.

If you want to get some value from server and combine it with javascript variables then do the following.

Use an ajax request and send the desired values to server. The server will return with a response. Use that response text and store it in your action variable.

How do I pass variables and data from PHP to JavaScript?

There are actually several approaches to do this. Some require more overhead than others, and some are considered better than others.

In no particular order:

  1. Use AJAX to get the data you need from the server.
  2. Echo the data into the page somewhere, and use JavaScript to get the information from the DOM.
  3. Echo the data directly to JavaScript.

In this post, we'll examine each of the above methods, and see the pros and cons of each, as well as how to implement them.

1. Use AJAX to get the data you need from the server

This method is considered the best, because your server side and client side scripts are completely separate.


  • Better separation between layers - If tomorrow you stop using PHP, and want to move to a servlet, a REST API, or some other service, you don't have to change much of the JavaScript code.
  • More readable - JavaScript is JavaScript, PHP is PHP. Without mixing the two, you get more readable code on both languages.
  • Allows for asynchronous data transfer - Getting the information from PHP might be time/resources expensive. Sometimes you just don't want to wait for the information, load the page, and have the information reach whenever.
  • Data is not directly found on the markup - This means that your markup is kept clean of any additional data, and only JavaScript sees it.


  • Latency - AJAX creates an HTTP request, and HTTP requests are carried over network and have network latencies.
  • State - Data fetched via a separate HTTP request won't include any information from the HTTP request that fetched the HTML document. You may need this information (e.g., if the HTML document is generated in response to a form submission) and, if you do, will have to transfer it across somehow. If you have ruled out embedding the data in the page (which you have if you are using this technique) then that limits you to cookies/sessions which may be subject to race conditions.

Implementation Example

With AJAX, you need two pages, one is where PHP generates the output, and the second is where JavaScript gets that output:


/* Do some operation here, like talk to the database, the file-session
* The world beyond, limbo, the city of shimmers, and Canada.
* AJAX generally uses strings, but you can output JSON, HTML and XML as well.
* It all depends on the Content-type header that you send with your AJAX
* request. */

echo json_encode(42); // In the end, you need to echo the result.
// All data should be json_encode()d.

// You can json_encode() any value in PHP, arrays, strings,
//even objects.

index.php (or whatever the actual page is named like)

<!-- snip -->
function reqListener () {

var oReq = new XMLHttpRequest(); // New request object
oReq.onload = function() {
// This is where you handle what to do with the response.
// The actual data is found on this.responseText
alert(this.responseText); // Will alert: 42
};"get", "get-data.php", true);
// ^ Don't block the rest of the execution.
// Don't wait until the request finishes to
// continue.
<!-- snip -->

The above combination of the two files will alert 42 when the file finishes loading.

Some more reading material

  • Using XMLHttpRequest - MDN
  • XMLHttpRequest object reference - MDN
  • How do I return the response from an asynchronous call?

2. Echo the data into the page somewhere, and use JavaScript to get the information from the DOM

This method is less preferable to AJAX, but it still has its advantages. It's still relatively separated between PHP and JavaScript in a sense that there is no PHP directly in the JavaScript.


  • Fast - DOM operations are often quick, and you can store and access a lot of data relatively quickly.


  • Potentially Unsemantic Markup - Usually, what happens is that you use some sort of <input type=hidden> to store the information, because it's easier to get the information out of inputNode.value, but doing so means that you have a meaningless element in your HTML. HTML has the <meta> element for data about the document, and HTML 5 introduces data-* attributes for data specifically for reading with JavaScript that can be associated with particular elements.
  • Dirties up the Source - Data that PHP generates is outputted directly to the HTML source, meaning that you get a bigger and less focused HTML source.
  • Harder to get structured data - Structured data will have to be valid HTML, otherwise you'll have to escape and convert strings yourself.
  • Tightly couples PHP to your data logic - Because PHP is used in presentation, you can't separate the two cleanly.

Implementation Example

With this, the idea is to create some sort of element which will not be displayed to the user, but is visible to JavaScript.


<!-- snip -->
<div id="dom-target" style="display: none;">
$output = "42"; // Again, do some operation, get the output.
echo htmlspecialchars($output); /* You have to escape because the result
will not be valid HTML otherwise. */
var div = document.getElementById("dom-target");
var myData = div.textContent;
<!-- snip -->

3. Echo the data directly to JavaScript

This is probably the easiest to understand.


  • Very easily implemented - It takes very little to implement this, and understand.
  • Does not dirty source - Variables are outputted directly to JavaScript, so the DOM is not affected.


  • Tightly couples PHP to your data logic - Because PHP is used in presentation, you can't separate the two cleanly.

Implementation Example

Implementation is relatively straightforward:

<!-- snip -->
var data = <?php echo json_encode("42", JSON_HEX_TAG); ?>; // Don't forget the extra semicolon!
<!-- snip -->

Good luck!

PHP Variable inside PHP - Echo - Javascript

You'll want to use string concatenation (using the . character) to insert a variable into your string. Like this:

echo '
<script type="text/javascript">
var dID = ' . $dID . ';
function wait(ms){

A . will concatenate two strings together. For example:

echo 'hello ' . ' world'

You can also insert a variable directly into a string, if you use double quotes. Single quotes do not allow you to do this:

$text = "world";
echo "hello $text";

In general, you should wrap your variables in curly brackets ({ and })

$text = "world";
echo "hello {$text}";

Set Javascript Variable From PHP Get Variable

Put your javascript code into a separate php file under script tag:



var custid = '<?php echo($custid); ?>';
var cardid = '<?php echo($cardid); ?>';



Include this file in your main php file (using the include function).
It is not possible to execute php in a separate .js file.

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