Question

So i have been trying to make my canvas game work in real time multiplayer with long polling right now which connects to my mysql database, but I am now trying to switch to web sockets. I am a little confused on where the websockets in storing information and on how it is being organized when it is stored. Do the websockets connect to a mysql server? Does the information stored using websockets reset when the server resets? any help is appreciated. Thanks

Answer 1

DISCLAIMER: This answer is directed to the OPs comments. The scripts presented are, by no means, secure. It’s preferable to use a third party FW like Ratchet

I think you’re misunderstanding how PHP works. Let me give you an example and build some explanation from that…

---

You have a webserver(example.com) with 2 files: a.php and b.php.

a.php

<?php
$varA = "I'm var A";
echo $varA;

b.php

<?php
echo $varA;

to run script a.php you direct the browser to http://example.com/a.php. Output is:

I’m var A

However going to http://example.com/b.php will print a notice saying

Notice: Undefined variable: varA in /path/to/webroot/b.php
on line 2

Why is that?

It’s because both script are totally independent. They dont’ even know of each other existence.

Now let’s change b.php a bit:

b.php

<?php
include 'a.php';
echo $varA;

output:

I’m var AI’m var A

This basically tells b.php to include a.php, thus “sharing” variables, objects, class and function definitions.

---

POST and GET

Another way to pass data between scripts is using POST or GET.

c.php

<?php
if (isset($_GET['c']) {
    $varC = $_GET['c'];
} else {
    $varC = 'NONE';
}
echo $varD;

Going to http://example.com/c.php will output

NONE

Going to http://example.com/c.php?c=something will output

something

Passing a variable from d.php to c.php. You can use a GET request.

d.php

<?php
$varD = urlencode("i'm from d");
echo "<a href=\"http://example.com/c.php?c=$varD\">pass value</a>";

or

header('Location: http://example.com/c.php?c='.urlencode("i'm from d"));

Going to d.php and clicking pass value will output

i’m from d

Instead of using GET you can do a POST request. (we will cover that later)

---

$_SESSION

What about between “accesses”?

Each time you access a php file, the script is run from the beginning to the end.

Here’s another file (e.php)

<?php
if (!isset($i)) {
    $i = 0;
}
++$i;

This script tells you that if var $i is not defined, $i=0 and then increments it by one.

Accessing http://example.com/e.php will ALWAYS output 1. No data is stored between accesses.

Unless… you use the $_SESSION variable (or store the data in a persistent media).

ii.txt

0

e.php

<?php
session_start();
if (!isset($_SESSION['i'])) {
    $_SESSION['i'] = 0;
}
++$_SESSION['i'];

$ii = file_get_contents('ii.txt');
++$ii;
file_put_contents('ii.txt', $ii);

echo "session counter: " . $_SESSION['i'];
echo '<br/>';
echo "file counter: " . $ii;

Each time you access e.php, both counters will increase.

BUT… $_SESSION variable is not a persistent media. When the session is destroyed (or expires), session counter will reset. However, the file counter will always increase, so it’s a persistent media. You can, of course, use a database to store the variable. The principle is the same.

---

Passing variables between different servers:

The principle is the same when passing variables between file in the same server. However, you can’t (normally) include or require a php file located in another server. Moreover, it is best when sending information from two locations to secure the data. Here’s an example using a socket connection.

a.php (located at client.com)

<?php
//Our Data
$dataArray = array('foo' => 'some data', "bar" => 42);

// Data convertion into URL parameters -> foo=some%20data&bar=42
$data = http_build_query($dataArray);

//extract the parts of the url 
$url = parse_url("http://server.com/b.php");

$host = $url['host']; //server.com
$path = $url['path']; //b.php

$fp = fsockopen($host, 80, $errno, $errstr, 30);

if ($fp) {

    //HEADERS
    fputs($fp, "POST $path HTTP/1.1\r\n"); //POST method
    fputs($fp, "Host: $host\r\n"); //The host
    fputs($fp, "Referer: myApp\r\n"); //who's the referer
    fputs($fp, "Content-type: application/x-www-form-urlencoded\r\n"); //Content type: a form post that is url encoded
    fputs($fp, "Content-length: ". strlen($data) ."\r\n"); //data length (size in chars)
    fputs($fp, "Connection: close\r\n\r\n");
    //DATA
    fputs($fp, $data);

    $result = '';
    // Request result
    while(!feof($fp)) {
        $result .= fgets($fp, 128);
    }
} else { 
    // Something went bad
    echo "ERROR: $errstr ($errno)";
}
// Socket close
fclose($fp);

//SUCCESS
// split the result header from the content
$result = explode("\r\n\r\n", $result, 2);
$header = isset($result[0]) ? $result[0] : '';
$content = isset($result[1]) ? $result[1] : '';

echo "HEADER: $header<br><br>";
echo "CONTENT:<br>$content";

b.php (located at server.com)

<?php
header('Content-type: text/plain');
if (isset($_POST)) {
    file_put_contents('data.txt', $_POST, FILE_APPEND);
    file_put_contents('data.txt', PHP_EOL, FILE_APPEND);
    print file_get_contents('data.txt');

} else {
    echo "NOT OK";
}

when going to http://client.com/a.php a POST request is sent to b.php. If it is successful, b.php stores the data in a file called data.txt and returns the contents of that file.

Hope this helps understanding sockets and PHP.