Cookies

Today, I learned about the "Cookies." 

 

A web application consists of a series of disconnected HTTP requests to a web server.

In HTTP, we can pass information using:

• Query Strings (URL, header)
• Hidden Form Fields

 

Use Query Strings to Save State Information

• Seperate individual name = value pairs within the query string using 
• Ap question mark (?) and a query string are automatically appended to the URL of a server-side script for any formas that are submitted with the GET method.
• Add a question mark immediately after a URL to pass information from one Web page to another.

ex)

<a href="http://www.URL.com/TargetPage.php?firstName=Don&lastName=Gosselin&occupation=writer:>Link Text</a>

 

Use Hidden From Fields

Create hidden form fields with the <input> element

• Temporarily store data that needs to be sent to server that a user does not need to see

<form action="CourseListings.php" method="get">
	<p><input type="submit" value="Register for Classes" />
	<input type="hidden" name="diverID" value="<? $DiverID ?>"/></p>
</form>

 

Now, we are gonna learn about the Cookies at the User.

Cookies

Cookies are a client-side approach for persisting state information.

They are name=value pairs that are saved within one or more text files that are managed by the browser.

One typical use of cookies in a website is to "remember" the visitor so that the server can customize the site for the user.

Cookies cannot be shared outside of a domain.

 

This is how cookies work.

 

Using Cookies in PHP

Cookies in PHP are created using the setcookie() function and are retrieved using the $_COOKIES superglobal associative array.

Cookies created without expirytime are temporary only for the current browser session.

Cookies must be written before any other page output.

// Writing a cookie
$expiryTime = time()+60*60*24;
//create a cookie
$name = "username";
$value = "Ricardo";
setcookie($name, $value, $expiryTime);

// Reading a cookie
if (!isset($_COOKIE['username'])){echo "this cookie doesn't exist";}
else {
	echo "The username retrieved from the cookie is: ".$_COOKIE['username'];
    }
    
// loop through all cookies in request
foreach ($_COOKIE as $name => $value){
	echo "Cookie: $name = $value";
}

 

Deleting Cookies

• To delete a persistent cookie before the time assigned to the expires argument elapse, assign a new expiration value that is sometime in the past
• Do this by subtracting any number of seconds from the time() function

setcookie("username","",time()-3600);

 

Law on cookies

Websites must:

• Tell people the cookies are there an what cookies are being used
• Explain what the cookies are doing and why, and
• Get the user;s consent to store a cookies on their device