How to access PHP variables located in external PHP file within Javascript code?

Question

I am a learning developer that is trying to utilize websockets, php and javascript to create a module for a web application I use. However, I am not sure if I can use the two languages together in such a way that I am doing as I am not very knowledgeable with Javascript yet.

What I would like to do is grab two strings located in a settings.php file, get those strings, convert those strings over to a Javascript string so that I can use what the PHP string value is as the Javascript variable. I tried to follow guides online and got this far with the browser console only showing

WebSocket connection to 'wss://%3C/?php%20echo%20$server_ip%20?%3E:%3C?php%20echo%20$server_port%20?%3E/websocket' failed: Error in connection establishment: net::ERR_NAME_NOT_RESOLVED

Followed guides similar to this including this one to try to gain an understanding with no luck: https://www.dyn-web.com/tutorials/php-js/scalar.php

This guide was suggested as similar, but this involves an external Javascript file and not an external PHP file. This is totally different. Access PHP var from external javascript file

Here is the main code in question where I'll access the PHP variable in Javascript:

    <!--Include some variables from PHP settings file to fetch IP/port-->
    <?php include(ROOT_PATH . '/modules/Webchat/includes/settings.php'); ?>
    <?php echo $server_ip; ?>

    <script type="text/javascript">
        $(document).ready(function(){
            var socket;
            if (!window.WebSocket) {
                window.WebSocket = window.MozWebSocket;
            }
            if (window.WebSocket) {


                var ip = "<?php echo $server_ip ?>";
                var port = "<?php echo $server_port ?>";
                // TODO: Get socketAddress from settings.php


                var socketAddress = ip + (port ? ':' + port : '');


                var nextID = 0;
                var messageCount = 0;

                socket = new WebSocket("wss://" + socketAddress + "/websocket");

Here is my settings.php file where the PHP variables are stored:

<?php
$server_ip = $queries->getWhere('mc_servers', array('is_default', '=', 1));
$server_port = 25566;
$endpoint = "/websocket";
?>

I expect the output of the server_ip php variable to be a string such as "server.example.com". I expect the output of server_port to be 25566.

Hello, I'm interested to know why you are using websockets and not AJAX to communicate with the server? — suspectus, Aug 11 '19 at 18:47
Possible duplicate of [Access PHP var from external javascript file](https://stackoverflow.com/questions/2928827/access-php-var-from-external-javascript-file) — Tom Wyllie, Aug 11 '19 at 18:51
If your seeing `%3C/?php%20echo%20$server_ip%20?%3E:%3C` then php is not working, you checked the filename is `.php` and not `.html`? — Lawrence Cherone, Aug 11 '19 at 18:58
when you look at source in the browser what does the line for `` near the top say? — akaBase, Aug 11 '19 at 19:01
@suspectus The server is written in Java using Jetty. I have also never worked with Ajax, though I read that it may have been a better method. For now, I'm just trying to get a working concept and then improve from that. — Victor L, Aug 11 '19 at 19:01
@VictorL no, you are trying to echo it out onto the page outside of the script tags, it would show on the page. — akaBase, Aug 11 '19 at 19:04
@akaBase Yeah, that is exactly what the `````` is for below the ``````. I was trying to find out the value of $server_ip but it returns nothing on the page. — Victor L, Aug 11 '19 at 19:06
@VictorL okay, so that means that you aren't getting the php file if there is a `$server_ip` variable on it, echo out the path to make sure its right. — akaBase, Aug 11 '19 at 19:08
Are you sure your web server supports PHP? A Java web server almost certainly won't. — , Aug 11 '19 at 19:11
@duskwuff Yes it supports PHP. I've already got a working concept using the application's standalone form on Java. I'm creating an external link to this Java application in PHP. The problem at hand is the variables. Javascript isn't grabbing the variable from PHP. The problem has nothing to do with my websocket links or connection, the connection is fine and my code works when I am not using the PHP variables. — Victor L, Aug 11 '19 at 19:15
@VictorL I think @duskwuff might be right, or you are trying to use PHP on a HTML file? as your error shows that the PHP opening tags are being treated as strings `'wss://?php echo $server_ip ?>:/websocket'` thats your error un-urlencoded. — akaBase, Aug 11 '19 at 19:32

score 0 · Answer 1 · answered Aug 11 '19 at 19:34

You could solve this by having the PHP file echo out the variables, then use javascript to request and load them.

Make sure that settings.php is accessible somewhere on the server and put

<?php
$server_ip = $queries->getWhere('mc_servers', array('is_default', '=', 1));
$server_port = 25566;
$endpoint = "/websocket";
header("Access-Control-Allow-Origin: *");
echo json_encode([$server_ip, $server_port, $endpoint]);
?>

The header keeps a CORS error from happening and then we encode the values as JSON.

<script type="text/javascript">
    $(document).ready(function(){
        var socket;
        if (!window.WebSocket) {
            window.WebSocket = window.MozWebSocket;
        }
        if (window.WebSocket) {
            $.getJSON('/modules/Webchat/includes/settings.php') 
              .done(function setvars(data) {
                  server_ip = data[0];
                  server_port = data[1];
                  endpoint = data[2];
              })
              .fail(function (data) {
                  alert('Couldn't get server variables! ')
              });

            var socketAddress = ip + (port ? ':' + port : '');

            var nextID = 0;
            var messageCount = 0;

            socket = new WebSocket("wss://" + socketAddress + "/websocket");
</script>

What this code does is it uses $.getJSON to retrieve the encoded variables from settings.php as load then as javascript variables

How to access PHP variables located in external PHP file within Javascript code?

1 Answers1