How cookies work in PHP - Practice Exercises

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP cookie code?

Consider this PHP script that sets a cookie and then tries to read it immediately:

<?php
setcookie('user', 'Alice', time() + 3600);
if (isset($_COOKIE['user'])) {
    echo 'User is ' . $_COOKIE['user'];
} else {
    echo 'No user cookie found';
}
?>

What will this script output when run for the first time in a browser?

PHP

<?php
setcookie('user', 'Alice', time() + 3600);
if (isset($_COOKIE['user'])) {
    echo 'User is ' . $_COOKIE['user'];
} else {
    echo 'No user cookie found';
}
?>

A User is Alice

B User is

C Error: Undefined index 'user'

D No user cookie found

💡 Hint

Remember that cookies are sent by the browser on the next request, not immediately.

When you set a cookie with setcookie(), it sends a header to the browser. The cookie is not available in $_COOKIE until the next page load because the browser must send it back in the request headers.

🧠 Conceptual

intermediate

Which HTTP header is used to set a cookie?

When a server wants to store a cookie on a user's browser, which HTTP response header does it use?

A Set-Cookie

B Content-Type

C Authorization

D Cookie

💡 Hint

Think about the header sent from server to client to store data.

The server uses the Set-Cookie header to tell the browser to store a cookie. The browser then sends the cookie back in the Cookie header on future requests.

❓ Predict Output

advanced

What is the output of this PHP cookie deletion code?

Look at this PHP code that tries to delete a cookie:

<?php
setcookie('session', '', time() - 3600);
if (isset($_COOKIE['session'])) {
    echo 'Session cookie exists';
} else {
    echo 'Session cookie deleted';
}
?>

What will this script output when run immediately after the cookie was set previously?

PHP

<?php
setcookie('session', '', time() - 3600);
if (isset($_COOKIE['session'])) {
    echo 'Session cookie exists';
} else {
    echo 'Session cookie deleted';
}
?>

A Error: Cannot delete cookie

B Session cookie exists

C Session cookie deleted

D Session cookie

💡 Hint

Think about when the cookie is actually removed from $_COOKIE.

Setting a cookie with a past expiration date tells the browser to delete it, but $_COOKIE still contains the cookie data for the current request. The cookie will be gone on the next request.

🔧 Debug

advanced

Why does this PHP cookie code cause a warning?

Consider this PHP code snippet:

<?php
setcookie('theme', 'dark');
echo $_COOKIE['theme'];
?>

When run, it sometimes shows a warning: Undefined index: theme. Why?

PHP

<?php
setcookie('theme', 'dark');
echo $_COOKIE['theme'];
?>

A Because the cookie is not available in $_COOKIE until the next request

B Because setcookie() does not actually set cookies

C Because $_COOKIE is read-only and cannot be accessed

D Because 'theme' is a reserved keyword in PHP

💡 Hint

Think about when cookies become available in PHP.

Cookies set by setcookie() are sent to the browser in headers. The browser sends them back on the next request. So, $_COOKIE does not contain the new cookie until the next page load.

🚀 Application

expert

How many cookies will be sent to the server?

A website sets these cookies with these paths:

• Cookie A: path=/
• Cookie B: path=/shop
• Cookie C: path=/shop/sale

If the browser requests the URL https://example.com/shop/sale/item1, how many cookies will be sent to the server?

A 1

B 2

C 3

D 0

💡 Hint

Cookies are sent if the request path starts with the cookie's path.

All three cookies have paths that match the request URL path. The request path /shop/sale/item1 starts with /, /shop, and /shop/sale, so all three cookies are sent.