How to pass data from Javascript to PHP and vice versa?


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))
1
11
7/19/2012 2:50:26 AM

Accepted Answer

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.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    httpc.setRequestHeader("Content-Length", params.length); // POST request MUST have a Content-Length header (as per HTTP/1.1)

    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 ;)

19
11/11/2018 7:54:24 PM

I run into a similar issue the other day. Say, I want to pass data from client side to server and write the data into a log file. Here is my solution:

My simple client side code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"   "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
   <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js" type="text/javascript"></script>
   <title>Test Page</title>
   <script>
    function passVal(){
        var data = {
            fn: "filename",
            str: "this_is_a_dummy_test_string"
        };

        $.post("test.php", data);
    }
    passVal();
   </script>

</head>
<body>
</body>
</html>

And php code on server side:

<?php 
   $fn  = $_POST['fn'];
   $str = $_POST['str'];
   $file = fopen("/opt/lampp/htdocs/passVal/".$fn.".record","w");
   echo fwrite($file,$str);
   fclose($file);
?>

Hope this works for you and future readers!


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