Wednesday, July 7, 2010

PHP Cookies

A cookie is often used to identify a user.

What is a Cookie?

A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.

How to Create a Cookie?

The setcookie() function is used to set a cookie.

Note: The setcookie() function must appear BEFORE the tag.


setcookie(name, value, expire, path, domain);


In the example below, we will create a cookie named "user" and assign the value "Alex Porter" to it. We also specify that the cookie should expire after one hour:

setcookie("user", "Alex Porter", time()+3600);

Note: The value of the cookie is automatically URLencoded when sending the cookie, and automatically decoded when received (to prevent URLencoding, use setrawcookie() instead).

How to Retrieve a Cookie Value?

The PHP $_COOKIE variable is used to retrieve a cookie value.

In the example below, we retrieve the value of the cookie named "user" and display it on a page:

// Print a cookie
echo $_COOKIE["user"];

// A way to view all cookies

In the following example we use the isset() function to find out if a cookie has been set:

if (isset($_COOKIE["user"]))
echo "Welcome " . $_COOKIE["user"] . "!
echo "Welcome guest!

How to Delete a Cookie?

When deleting a cookie you should assure that the expiration date is in the past.

Delete example:

// set the expiration date to one hour ago
setcookie("user", "", time()-3600);

What if a Browser Does NOT Support Cookies?

If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. One method is to pass the data through forms (forms and user input are described earlier in this tutorial).

The form below passes the user input to "welcome.php" when the user clicks on the "Submit" button:


Retrieve the values in the "welcome.php" file like this:

Welcome .

You are years old.

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