How to call Javascript function in PHP?

I have a JavaScript function from which I need to call a PHP function written in a separate file. How can I do this?

• The PHP function returns a value that I want to assign to a JavaScript variable.

• Answer:

  Assuming you can modify the code in both files: Turn the PHP function into a web service which accepts arguments by URL and dumps its output to the HTTP response. Then call the service with an AJAX request and stick the response into your variable. <?php // http://example.com/add.php function add($a, $b) { header('Content-type: text/json'); echo json_encode(array('sum' => $a + $b)); } add($_GET['a'], $_GET['b']); ?> // This is jQuery, but it could be anything $.getJSON('http://example.com/add.php?a=2&b=2', function(response) { doSomethingWith(response.sum); }); Now all your components are decoupled, but they can still access each other with a well-known interface. (You could also call sum() from another language in the same way if you wanted to, and everything supports JSON these days.) If for some reason that approach won't work, you could do the same sort of thing with JSONP: <?php function add() { // ... work omitted echo $_GET['functionToCall'] + "($sum)"; } ?> // Your Javascript function useSum(sumFromServer) { // Do something with it } <!-- In your HTML: --> <script src="http://example.com/add.php?a=2&b=2&functionToCall=useSum"></script> ---- [1] Please keep in mind this demo code is insecure. In production, you'll at least want to filter the input.