PHP variable in JavaScript is not getting updated

Question

I'm trying to pass a PHP variable (number) to JavaScript. It kind of works but as soon as the number changes, it's not getting updated. My code:

 $totalamount = $woocommerce->cart->get_total(); 
 $totalamount = preg_replace("/[^0-9\.]/", "", $totalamount);
 $totalamount = number_format($totalamount, 2, '.', '');
 var_dump($totalamount);
?>
<script type="text/javascript">
 var Amount = "<?php echo $totalamount; ?>"

In the var_dump($totalamount); the number get's updated every time. In JavaScript it gives 0 after a change.

What is the proper way to pass a variable to JavaScript so it gets updated?

• j08691: Unless you reload the page or use AJAX, your variable will only update the first time.
• Shimon Rachlenko: How do you change the number?
• Matthew: Can you be a bit more clear about what your expecting to happen? The number in $totalamount will be generated when the page loads and outputted to the javascript. Or are you saying that on the page load, the var_dump outputs the correct number but the echo totalamount doesn't?

Answer 1

PHP is a server side language which means it is only executed at the time the page is loading, and the code will not be re-run unless you refresh the page.

To get around this you can retrive the total using an AJAX call which would get the total in the background and then update the page.

To get started with Ajax here is a good tutorial: Ajax

• Trekdrop: I know. However the page is getting reloaded after a change so I thougth this could work. Can you explain me why the variable in the var_dump is getting updated after a page reload, but not in the js? Edit Probably the is not getting reloaded. It's works indeed if I do a reload myself (F5). However, the number in the var_dump is changed when I come back to the page.. not clear yet.
• 1321941: @LarsKerff can you check the web console and see if there are any errors showing up? Is there any other code in between the var_dump and the js? If you try to echo the amount again after the js does it show the right value?
• Trekdrop: Nope, no errors. If I place a echo after the js, it's shows also the right value.
• 1321941: @LarsKerff hmm, it looks like you are passing it right. How are you checking its value?
• Trekdrop: the value is shown in a document.write expression: document.write("<input type=\"hidden\" NAME=\"amount\" value=\"" + Amount + "\" />"); It's not in the same file.