Basic PHP Crash Course (part 4)

Tuesday, April 3, 2012

This post is part 4 of the Basic PHP Crash Course. If you have never red before this Crash Course, you should read part 1, part 2 and part 3 first. In this post we will discuss about PHP Session. It is very useful when you write a web application. Let's think about our pizza shop website. After the user have submitted the order form, our application will call the process.php. Then I want to show the order form again, if the submitted form has the errors. To do so, we have a problem. We cannot know the error data from process.php when we show the order form again. So we must use PHP Session.

What is PHP Session?

Session is a way to store information for the individual user in our server by using session ID. This ID is automatically generated by PHP and store also on the user computer for the lifetime of a session. The content of the session data is store at the server.

Simple Example

<?php session_start(); ?>
<html>
<head>
 <title>Page 1</title>
</head>
<body>
<?php
 $_SESSION['user_name'] = "John";
?>
</body>
</html>

Before we use the session data, we need to load session_start() function. This function will check whether there is already a session. If not, it will create one. Now we can use the superglobal $_SESSION array. So I set the user_name as John. Below is the another page.

<?php session_start(); ?>
<html>
<head>
 <title>Page 2</title>
</head>
<body>
<?php
 echo "Hi ".$_SESSION['user_name'];
?>
</body>
</html>

In this page, we echo the user_name from session data array. If you run the page2, you will see "Hi John". In this way, you can save the data you need for other page. However session data is not permanent storage. For permanent storage, we will use the database like MySql(I will also explain about MySql database later in this series.).

Enhancing our pizza shop website

Now it is time to enhance our pizza shop site. Below is our index.php.

<?php session_start(); ?>
<html>
<head>
 <title>Order Process</title>
</head>
<body>
<?php
 if(isset($_POST['submit']))
 {
  if( $_POST['cus_name'] != '' && $_POST['quantity'] != '' && $_POST['address'] !='' )
  {
   $cus_name = $_POST['cus_name'];
   $quantity = $_POST['quantity'];
   $address = $_POST['address'];
?>
 <p>Thank <?php echo $cus_name; ?> !</p>
 <p>You order <?php echo $quantity; ?> pizza.</p>
<?php
 $total = $quantity * 10;
?>
 <p>It will cost you <?php echo $total; ?> $.</p>
 <p>We will send withing 2 hours to <?php echo $address; ?>.</p>
<?php
 }
 else
 {
  $_SESSION['error'] = "You need to fill all data.";
  header("location: index.php");
 }
?>
<?php } ?>
</body>
</html>

As you know, firstly we need to call the session_start() function to use the session data. If the user submit the form without filling all data, we will set the session error data as "You need to fill all data.". And then redirect our site to index.php by using header() function. This function will tell the browser to load the page that you send as parameter. In our index.php file, we will also start with session_start() function. Then we will retrieve the error data from the session array and will echo before our order form. Below is our index.php.

<?php session_start(); ?>
<html>
<head>
 <title>Pizzs Show: Home</title>
</head>
<body>
<?php 
 if($_SESSION['error'] != '')
 {
  echo $_SESSION['error']; 
  $_SESSION['error']='';
 }
?>
 <h3>Pizza Shop Order Form</h3>
 <form action="process.php" method="post">
 <p>
  <label for="cus_name">Customer Name:</label>
  <input type="text" name="cus_name" />
 </p>
 <p>
  <label for="address">Shipping Address:</label>
  <input type="text" name="address" />
 </p>
 <p>
  <label for="quantity">Pizza Quantity:</label>
  <input type="text" name="quantity" />
 </p>
 <p>
  <input type="submit" name="submit" value="Submit Order" />
 </p>
 </form>
</body>
</html>

TutsforWeb

Pages

Basic PHP Crash Course (part 4)

What is PHP Session?

Simple Example

Enhancing our pizza shop website

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