Setting and reading cookies in PHP - Mini Project: Build & Apply

Setting and Reading Cookies in PHP

📖 Scenario: You are building a simple website that remembers a visitor's favorite color using cookies. When the visitor selects a color, the website saves it in a cookie. When the visitor returns, the website reads the cookie and shows the favorite color.

🎯 Goal: Create a PHP script that sets a cookie named favorite_color with a specific value, then reads and displays the cookie value if it exists.

📋 What You'll Learn

Create a cookie named favorite_color with the value blue

Set the cookie to expire in 1 hour

Check if the cookie favorite_color exists

Display the message Your favorite color is: blue if the cookie exists

Display No favorite color set if the cookie does not exist

💡 Why This Matters

🌍 Real World

Cookies are used on websites to remember user preferences, login status, and other information to improve user experience.

💼 Career

Web developers often need to set and read cookies to manage sessions, personalize content, and track user behavior.

1

Create a cookie named favorite_color

Write a line of PHP code to set a cookie named favorite_color with the value blue that expires in 1 hour using the setcookie function.

PHP

<?php
// Set a cookie named favorite_color with value blue that expires in 1 hour
// Your code here

Hint

Use setcookie("favorite_color", "blue", time() + 3600); to set the cookie.

2

Check if the cookie favorite_color exists

Add an if statement to check if the cookie favorite_color exists in the $_COOKIE superglobal array.

PHP

<?php
setcookie("favorite_color", "blue", time() + 3600);

// Check if the cookie favorite_color exists
// Your code here

Hint

Use isset($_COOKIE["favorite_color"]) to check if the cookie is set.

3

Display the favorite color if the cookie exists

Inside the if block, write a print statement to display Your favorite color is: followed by the cookie value $_COOKIE["favorite_color"]. Add an else block that prints No favorite color set.

PHP

<?php
setcookie("favorite_color", "blue", time() + 3600);

if (isset($_COOKIE["favorite_color"])) {
    // Print favorite color
    // Your code here
} else {
    // Print no favorite color message
    // Your code here
}

Hint

Use print("Your favorite color is: " . $_COOKIE["favorite_color"]) inside the if and print("No favorite color set") inside the else.

4

Run the script and see the output

Run the complete PHP script and observe the output. It should print Your favorite color is: blue if the cookie is set, or No favorite color set if not.

PHP

<?php
setcookie("favorite_color", "blue", time() + 3600);

if (isset($_COOKIE["favorite_color"])) {
    print("Your favorite color is: " . $_COOKIE["favorite_color"]);
} else {
    print("No favorite color set");
}

// Run the script and check output
// Your code here

Hint

Run the script in a browser or PHP server to see the cookie message.

Practice

1. What is the main purpose of using cookies in PHP?

easy

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

B. To execute server-side scripts

C. To connect to a database

D. To style the webpage

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 A

4. Quick Check:

   Cookies = store small data [OK]

Hint: Cookies save small data on user devices [OK]

Common Mistakes:

• Confusing cookies with server-side code execution
• Thinking cookies connect to databases
• Assuming cookies control webpage style

2. Which of the following is the correct way 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 correct function name and syntax

   The PHP function to set cookies is setcookie(), which takes the cookie name and value as strings.

2. Step 2: Check the options for correct syntax

   Only setcookie('user', 'John'); uses the correct function name and quotes around name and value.

3. Final Answer:

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

4. Quick Check:

   Use setcookie() with quoted strings [OK]

Hint: Use setcookie() with quotes around name and value [OK]

Common Mistakes:

• Using wrong function names like cookie_set or set_cookie
• Not quoting the cookie name and value
• Confusing cookie setting with reading

3. What will be the output of the following PHP code if the cookie color is set to blue?

<?php
if (isset($_COOKIE['color'])) {
    echo $_COOKIE['color'];
} else {
    echo 'No color set';
}
?>

medium

A. color

B. No color set

C. Error: Undefined index

D. blue

Solution

1. Step 1: Check if the cookie 'color' exists

   The code uses isset() to check if $_COOKIE['color'] is set. Since the cookie is set to 'blue', this condition is true.

2. Step 2: Output the cookie value

   Because the cookie exists, the code echoes its value, which is 'blue'.

3. Final Answer:

   blue -> Option D

4. Quick Check:

   Cookie exists, so output its value [OK]

Hint: Check isset before reading cookie to avoid errors [OK]

Common Mistakes:

• Assuming cookie is not set and printing default
• Not using isset and causing undefined index error
• Confusing cookie name with its value

4. Identify the error in this PHP code that tries to read a cookie named session:

<?php
echo $_COOKIE['session'];
?>

medium

A. Cookie name should be uppercase

B. Wrong function used to read cookie

C. Missing check if cookie exists before reading

D. Cookies cannot be read in PHP

Solution

1. Step 1: Understand cookie reading best practice

   Directly accessing $_COOKIE['session'] without checking if it exists can cause an undefined index notice if the cookie is not set.

2. Step 2: Identify the missing check

   The code should use isset($_COOKIE['session']) before echoing to avoid errors.

3. Final Answer:

   Missing check if cookie exists before reading -> Option C

4. Quick Check:

   Always check isset() before reading cookie [OK]

Hint: Always check isset() before using $_COOKIE values [OK]

Common Mistakes:

• Ignoring isset() check causing warnings
• Thinking cookie names are case sensitive in $_COOKIE
• Believing cookies cannot be read in PHP

5. You want to set a cookie named theme with value dark that expires in 7 days. Which code correctly sets this cookie?

hard

A. setcookie('theme', 'dark', time() + 60);

B. setcookie('theme', 'dark', time() + 7 * 24 * 60 * 60);

C. setcookie('theme', 'dark', 7);

D. setcookie('theme', 'dark', time() - 7 * 24 * 60 * 60);

Solution

1. Step 1: Calculate expiration time for 7 days

   7 days in seconds = 7 * 24 hours * 60 minutes * 60 seconds = 604800 seconds.

2. Step 2: Use time() plus 7 days for expiration

   The expiration parameter in setcookie() should be current time plus 604800 seconds.

3. Step 3: Check options for correct expiration

   setcookie('theme', 'dark', time() + 7 * 24 * 60 * 60); correctly uses time() + 7 * 24 * 60 * 60. setcookie('theme', 'dark', time() + 60); sets only 60 seconds, C uses 7 (invalid), D sets a past time (cookie expires immediately).

4. Final Answer:

   setcookie('theme', 'dark', time() + 7 * 24 * 60 * 60); -> Option B

5. Quick Check:

   Expire = now + 7 days in seconds [OK]

Hint: Expire time = time() + days * 86400 seconds [OK]

Common Mistakes:

• Using small numbers like 7 or 60 instead of seconds
• Setting expiration in the past
• Forgetting to add time() to expiration