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Archive for the ‘PHP Guide’ Category

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Retrieving Your Fresh Cookie

Tuesday, July 15th, 2008

If your cookie hasn’t expired yet, let’s retrieve it from the user’s PC using the aptly named $_COOKIE associative array. The name of your stored cookie is the key and will let you retrieve your stored cookie value!

PHP Code:

<?php
if(isset($_COOKIE['lastVisit']))
	$visit = $_COOKIE['lastVisit'];
else
	echo “You’ve got some stale cookies!”;

echo “Your last visit was - “. $visit;
?>

This handy script first uses the isset function to be sure that our “lastVisit” cookie still exists on the user’s PC, if it does, then the user’s last visit is displayed. If the user visited our site on February 28, 2008 it might look something like this:

Display:

Your last visit was - 11:48 - 02/28/08
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PHP: Creating Your First PHP Cookie

Tuesday, July 15th, 2008

When you create a cookie, using the function setcookie, you must specify three arguments. These arguments are setcookie(name, value, expiration):

  1. name: The name of your cookie. You will use this name to later retrieve your cookie, so don’t forget it!
  2. value: The value that is stored in your cookie. Common values are username(string) and last visit(date).
  3. expiration: The date when the cookie will expire and be deleted. If you do not set this expiration date, then it will be treated as a session cookie and be removed when the browser is restarted.

In this example we will be creating a cookie that stores the user’s last visit to measure how often people return to visit our webpage. We want to ignore people that take longer than two months to return to the site, so we will set the cookie’s expiration date to two months in the future!

PHP Code:

<?php
//Calculate 60 days in the future
//seconds * minutes * hours * days + current time
$inTwoMonths = 60 * 60 * 24 * 60 + time();
setcookie(’lastVisit’, date(”G:i - m/d/y”), $inTwoMonths);
?>

Don’t worry if you can’t follow the somewhat involved date calculations in this example. The important part is that you know how to set a cookie, by specifying the three important arguments: name, value and expiration date.

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PHP: Cleaning and Destroying your Session

Tuesday, July 15th, 2008

Although a session’s data is temporary and does not require that you explicitly clean after yourself, you may wish to delete some data for your various tasks.

Imagine that you were running an online business and a user used your website to buy your goods. The user has just completed a transaction on your website and you now want to remove everything from their shopping cart.

PHP Code:

<?php
session_start();
if(isset($_SESSION['cart']))
    unset($_SESSION['cart']);
?>

You can also completely destroy the session entirely by calling the session_destroy function.

PHP Code:

<?php
session_start();
session_destroy();
?>
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PHP Sessions: Using PHP’s isset Function

Tuesday, July 15th, 2008

Now that you know can easily store and retrieve data from the $_SESSION array, we can now explore some of the real functionality of sessions. When you create a variable and store it in a session, you probably want to use it in the future. However, before you use a session variable it is necessary that you check to see if it exists already!

This is where PHP’s isset function comes in handy. isset is a function that takes any variable you want to use and checks to see if it has been set. That is, it has already been assigned a value.

With our previous example, we can create a very simple pageview counter by using isset to check if the pageview variable has already been created. If it has we can increment our counter. If it doesn’t exist we can create a pageview counter and set it to one. Here is the code to get this job done:

PHP Code:

<?php
session_start();
if(isset($_SESSION['views']))
    $_SESSION['views'] = $_SESSION['views']+ 1;
else
    $_SESSION['views'] = 1;

echo “views = “. $_SESSION['views'];
?>

The first time you run this script on a freshly opened browser the if statement will fail because no session variable views would have been stored yet. However, if you were to refresh the page the if statement would be true and the counter would increment by one. Each time you reran this script you would see an increase in view by one.

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PHP: Storing a Session Variable

Tuesday, July 15th, 2008

When you want to store user data in a session use the $_SESSION associative array. This is where you both store and retrieve session data. In previous versions of PHP there were other ways to perform this store operation, but it has been updated and this is the correct way to do it.

PHP Code:

<?php
session_start();
$_SESSION['views'] = 1; // store session data
echo “Pageviews = “. $_SESSION['views']; //retrieve data
?>

Display:

Pageviews = 1

In this example we learned how to store a variable to the session associative array $_SESSION and also how to retrieve data from that same array.

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