$_SESSION doesn't seem to work across files? - php

Question

I am making a game for my computing class. The user has to change settings of their robot before playing. Most are using Visual Basic or Game Maker but I felt more comfortable with web based languages.
The issue I have just run into is when I am checking whether $_SESSION variables are set. This is a screenshot of my script:
http://i60.tinypic.com/2ia4hnr.jpg
As you can see on the left their is a button called "Play". On the customisation page the user fills in all the settings and they are stored as $_SESSION variables however when I use the If statement on all other pages it always sees them as not being set, so it does not allow them to play.
This is the customise.php page code (sorry for posting all the code but I felt it was needed for me to best explain my issue):
<?php $layout_context = "public"; ?>
<?php include("header.php"); ?>
<div id="main">
<div id="navigation">
<h2><i><u>Navigation</u></i></h2>
<br />
<u>Welcome<br /><br />
<u>How to Play?</u><br /><br />
<u><font color="orange">Customisation</font></u><br /><br />
<?php if (isset($_SESSION['RobotName'], $_SESSION['traction'], $_SESSION['passenger'])) {
?>
<u>Play</u>
<?php
} else {
?>
<u>Play</u>
<?php
}
?>
</div>
<div id="page">
<h1>Robot Customisation</h1>
<br />
<p><h3>Welcome to the BotMod Robot Customisation!</h3><br />
Below you will have three options that enable you to play BotMod. Those are: Your Robot name, Traction Type and Passenger Size.<br /> See the bottom of this page for further guidance.<br /><br />
<br />
<form id="settings" name="settings" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<h4>Robot Name:</h4> <input type="text" name="RobotName"><br />
<h4>Traction Type:</h4>
<select name="traction">
<option value="">Please Select Your Traction Type...</option>
<option value="Wheels">Wheels</option>
<option value="Tracks">Tracks</option>
<option value="Skis">Skis</option>
</select>
<br />
<h4>Passenger Size:</h4>
<select name="passenger">
<option value="">Please Select Your Passenger Size...</option>
<option value="Large">Large</option>
<option value="Medium">Medium</option>
<option value="Small">Small</option>
</select>
<br />
<input type="submit" name="Submit" value="Save Settings" />
</form>
<?php
require_once("session_start.php");
// Store all submitted $_POST fields to their own $_SESSION ID to be called
// later. Must use session_start();
if (isset($_POST['Submit']) && $_POST['RobotName'] != '' && $_POST['traction'] != '' && $_POST['passenger'] != '') {
$_SESSION['RobotName'] = $_POST['RobotName'];
$_SESSION['traction'] = $_POST['traction'];
$_SESSION['passenger'] = $_POST['passenger'];
} elseif (isset($_POST['Submit'])) {
echo "<br />";
echo "<br />";
echo "<strong>Error: You must complete all fields on this page!</strong><br />";
}
?>
<br />
<style>
div.container
{
width:30em;
border:1em solid;
}
div.box
{
box-sizing:border-box;
-moz-box-sizing:border-box; /* Firefox */
width: 50%;
border: 1em solid red;
float: left;
}
</style>
<?php if (isset($_POST['Submit']) && $_POST['RobotName'] != '' && $_POST['traction'] != '' && $_POST['passenger'] != '') {
echo "<h4>Your Settings (Click Play BotMod) to begin.</h4>";
?>
<div class="container">
<div class="box"><strong><i>Robot Name:</i></strong> <?php echo $_SESSION['RobotName']; ?><br /></div>
<div class="box"><strong><i>Traction:</i></strong> <?php echo $_SESSION['traction']; ?><br /></div>
<div class="box"><strong><i>Passenger:</i></strong> <?php echo $_SESSION['passenger']; ?><br /></div>
<div class="box"><strong>Play BotMod</strong><br /></div>
<div style="clear: both;"></div>
</div>
<?php
}
?>
</div>
</div>
<?php include("footer.php"); ?>
As you can see I have created an If statement on the play navigation.
<?php if (isset($_SESSION['RobotName'], $_SESSION['traction'], $_SESSION['passenger'])) {
?>
<u>Play</u>
<?php
} else {
?>
<u>Play</u>
<?php
}
?>
This doesn't work on any of the pages: customise.php index.php or instructions.php.
I have created the variables on the customise.php page with this code:
If (isset($_POST['Submit']) && $_POST['RobotName'] != '' && $_POST['traction'] != '' && $_POST['passenger'] != '') {
$_SESSION['RobotName'] = $_POST['RobotName'];
$_SESSION['traction'] = $_POST['traction'];
$_SESSION['passenger'] = $_POST['passenger'];
} elseif (isset($_POST['Submit'])) {
echo "<br />";
echo "<br />";
echo "<strong>Error: You must complete all fields on this page!</strong><br />";
}
?>
My index.php navigation code:
<u><font color="orange">Welcome</font><br /><br />
<u>How to Play?</u><br /><br />
<u>Customisation</u><br /><br />
<?php require_once("session_start.php"); ?>
<?php if (isset($_SESSION['RobotName'], $_SESSION['traction'], $_SESSION['passenger'])) {
?>
<u>Play</u>
<?php
} else {
?>
<u>Play</u>
<?php
}
?>
So does anyone know why the $_SESSION variables do not seem to work? I am using MAMP for this at the moment just in case that has something to do with it.

Answer 1

session_start(); must be called at the top of every page where you use the $_SESSION variable.
Documentation: http://php.net/function.session-start

Answer 2

use session start method
example :
session_start();

Answer 3

You need to call session_start() before accessing any session variables