How cookies work in PHP - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a cookie named 'user' with value 'John'.

PHP

<?php
setcookie([1], 'John');
?>

Drag options to blanks, or click blank then click option'

A'user'

B'username'

C'session'

D'cookie'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong cookie name like 'username' or 'session'.

Forgetting to put the cookie name in quotes.

The setcookie function requires the cookie name as the first argument. Here, the cookie name is 'user'.

2fill in blank

medium

Complete the code to retrieve the value of the cookie named 'user'.

PHP

<?php
if(isset($_COOKIE[[1]])) {
    echo $_COOKIE['user'];
}
?>

Drag options to blanks, or click blank then click option'

A'session'

B'cookie'

C'user'

D'username'

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for a cookie with a different name.

Not using quotes around the cookie name.

To check if the cookie named 'user' exists, use isset($_COOKIE['user']).

3fill in blank

hard

Fix the error in the code to set a cookie that expires in 1 hour.

PHP

<?php
setcookie('user', 'John', [1]);
?>

Drag options to blanks, or click blank then click option'

Atime() * 3600

B3600

Ctime() - 3600

Dtime() + 3600

Attempts:

3 left

💡 Hint

Common Mistakes

Using just 3600 instead of a timestamp.

Using a past time like time() - 3600.

The third argument of setcookie is the expiration time as a Unix timestamp. Use time() + 3600 for 1 hour from now.

4fill in blank

hard

Fill both blanks to set a cookie named 'theme' with value 'dark' that expires in 7 days.

PHP

<?php
setcookie([1], [2], time() + 7 * 24 * 3600);
?>

Drag options to blanks, or click blank then click option'

A'theme'

B'dark'

C'light'

D'color'

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the name and value.

Using wrong strings for name or value.

The cookie name is 'theme' and the value is 'dark'. The expiration is set to 7 days from now.

5fill in blank

hard

Fill all three blanks to delete the cookie named 'user'.

PHP

<?php
setcookie([1], [2], [3]);
?>

Drag options to blanks, or click blank then click option'

A'user'

B''

Ctime() - 3600

D'John'

Attempts:

3 left

💡 Hint

Common Mistakes

Not setting expiration to a past time.

Leaving the value as the old cookie value.

To delete a cookie, set its expiration time to a past time (like time() - 3600) and set its value to an empty string.

Practice

1. What is the primary purpose of cookies in PHP?

easy

A. To execute server-side scripts

B. To style web pages dynamically

C. To create database connections

D. To store small pieces of data on the user's computer

Solution

1. Step 1: Understand what cookies do

   Cookies save small data on the user's computer to remember information like preferences or login status.

2. Step 2: Identify the correct purpose

   Among the options, only storing small data on the user's computer matches the purpose of cookies.

3. Final Answer:

   To store small pieces of data on the user's computer -> Option D

4. Quick Check:

   Cookies store data = B [OK]

Hint: Cookies save data on user device, not server tasks [OK]

Common Mistakes:

• Confusing cookies with server-side code execution
• Thinking cookies style web pages
• Assuming cookies manage database connections

2. Which of the following is the correct syntax to set a cookie named user with value John in PHP?

easy

A. setcookie('user', 'John');

B. cookie_set('user', 'John');

C. set_cookie('user', 'John');

D. setcookie(user, John);

Solution

1. Step 1: Recall the PHP function to set cookies

   The correct PHP function is setcookie() with parameters as strings.

2. Step 2: Check syntax correctness

   setcookie('user', 'John'); uses correct function name and quotes around parameters, making it valid syntax.

3. Final Answer:

   setcookie('user', 'John'); -> Option A

4. Quick Check:

   Correct function and quotes = A [OK]

Hint: Use setcookie() with quoted strings for name and value [OK]

Common Mistakes:

• Using wrong function names like cookie_set or set_cookie
• Forgetting quotes around cookie name or value
• Passing variables without quotes incorrectly

3. What will be the output of the following PHP code?

setcookie('color', 'blue');
if(isset($_COOKIE['color'])) {
    echo $_COOKIE['color'];
} else {
    echo 'No cookie set';
}

medium

A. blue

B. No cookie set

C. Undefined index error

D. Syntax error

Solution

1. Step 1: Understand when cookies are available

   Cookies set by setcookie() are available on the next page load, not immediately in the same script.

2. Step 2: Check the condition in the code

   Since the cookie is not yet set in $_COOKIE during this script run, isset($_COOKIE['color']) is false, so it prints 'No cookie set'.

3. Final Answer:

   No cookie set -> Option B

4. Quick Check:

   Cookie available next request = A [OK]

Hint: Cookies appear in $_COOKIE on next page load, not immediately [OK]

Common Mistakes:

• Expecting cookie immediately after setcookie() in same script
• Assuming $_COOKIE is updated instantly
• Confusing cookie setting with session variables

4. Identify the error in this PHP code snippet that tries to set a cookie:

setcookie('theme', 'dark', time() + 3600)
echo 'Cookie set!';

medium

A. Missing semicolon after setcookie() call

B. Incorrect function name

C. Wrong parameter order in setcookie()

D. Cookies cannot be set with expiration time

Solution

1. Step 1: Check PHP syntax rules

   Each PHP statement must end with a semicolon (;). The setcookie() call is missing this.

2. Step 2: Verify function name and parameters

   The function name and parameters are correct, and expiration time is valid.

3. Final Answer:

   Missing semicolon after setcookie() call -> Option A

4. Quick Check:

   Semicolon missing = C [OK]

Hint: Always end PHP statements with semicolon [OK]

Common Mistakes:

• Forgetting semicolon at end of function calls
• Thinking expiration time is invalid
• Confusing function names

5. You want to create a cookie that lasts for 7 days, is only accessible over HTTPS, and cannot be accessed by JavaScript. Which of the following setcookie() calls correctly achieves this?

hard

A. setcookie('session', 'active', time() + 604800);

B. setcookie('session', 'active', time() + 604800, '/', '', false, true);

C. setcookie('session', 'active', time() + 604800, '/', '', true, true);

D. setcookie('session', 'active', time() + 604800, '/', '', true, false);

Solution

1. Step 1: Calculate expiration time for 7 days

   7 days = 7 * 24 * 3600 = 604800 seconds, so time() + 604800 is correct.

2. Step 2: Set secure and httponly flags

   To make cookie HTTPS-only, set the secure flag to true. To improve security, httponly should also be true.

3. Step 3: Check options

   setcookie('session', 'active', time() + 604800, '/', '', true, true); sets secure and httponly to true, matching requirements. Others either disable secure or httponly or omit parameters.

4. Final Answer:

   setcookie('session', 'active', time() + 604800, '/', '', true, true); -> Option C

5. Quick Check:

   Secure and httponly true for HTTPS cookie = D [OK]

Hint: Use secure=true and httponly=true for HTTPS cookies [OK]

Common Mistakes:

• Not setting secure flag to true for HTTPS-only cookies
• Omitting httponly flag for security
• Incorrect expiration time calculation