Question

How do I pass have a Javascript script request a PHP page and pass data to it? How do I then have the PHP script pass data back to the Javascript script?

client.js:

data = {tohex: 4919, sum: [1, 3, 5]}; // how would this script pass data to server.php and access the response? 

server.php:

$tohex = ... ; // How would this be set to data.tohex? $sum = ...; // How would this be set to data.sum? // How would this be sent to client.js? array(base_convert($tohex, 16), array_sum($sum)) 

Answer 1

Passing data from PHP is easy, you can generate JavaScript with it. The other way is a bit harder – you have to invoke the PHP script by a Javascript request.

An example (using traditional event registration model for simplicity):

<!-- headers etc. omitted --> <script> function callPHP(params) {     var httpc = new XMLHttpRequest(); // simplified for clarity     var url = 'get_data.php';     httpc.open('POST', url, true); // sending as POST      httpc.onreadystatechange = function() { //Call a function when the state changes.         if(httpc.readyState == 4 && httpc.status == 200) { // complete and no errors             alert(httpc.responseText); // some processing here, or whatever you want to do with the response         }     };     httpc.send(params); } </script> <a href='#' onclick='callPHP('lorem=ipsum&foo=bar')'>call PHP script</a> <!-- rest of document omitted --> 

Whatever get_data.php produces, that will appear in httpc.responseText. Error handling, event registration and cross-browser XMLHttpRequest compatibility are left as simple exercises to the reader 😉

See also Mozilla’s documentation for further examples