Starting and using sessions in PHP - Mini Project: Build & Apply

Starting and Using Sessions in PHP

📖 Scenario: You are building a simple website where users can log in. To remember who is logged in, you will use PHP sessions. Sessions help keep information about the user while they browse different pages.

🎯 Goal: Create a PHP script that starts a session, stores a username in the session, and then reads and displays that username on the page.

📋 What You'll Learn

Start a session using session_start()

Store a username in the $_SESSION superglobal array

Retrieve and display the username from the session

💡 Why This Matters

🌍 Real World

Sessions are used on websites to remember who a user is after they log in, so they don't have to enter their information on every page.

💼 Career

Understanding sessions is important for web developers to manage user login states and personalize user experiences.

1

Start a session

Write session_start(); at the top of your PHP script to begin a session.

PHP

Hint

Sessions must be started before any HTML or output is sent.

2

Store a username in the session

After session_start();, add the line $_SESSION['username'] = 'Alice'; to save the username 'Alice' in the session.

PHP

Hint

Use the $_SESSION array to save data that you want to keep across pages.

3

Retrieve the username from the session

Add a line to get the username from the session using $user = $_SESSION['username'];.

PHP

Hint

Assign the session value to a variable to use it easily later.

4

Display the username

Write echo "Logged in user: $user"; to show the username stored in the session.

PHP

Hint

Use echo to print the username on the page.

Practice

1. What is the main purpose of using session_start() in PHP?

easy

A. To begin a session and enable storing data across pages

B. To end a session and clear all session data

C. To connect to a database for user authentication

D. To send cookies to the user's browser

Solution

1. Step 1: Understand what session_start() does

   This function initializes a session or resumes the current one based on a session identifier passed via a cookie or URL.

2. Step 2: Recognize session purpose

   Sessions allow data to be saved and accessed across multiple pages for the same user, such as login status or preferences.

3. Final Answer:

   To begin a session and enable storing data across pages -> Option A

4. Quick Check:

   session_start() starts session = D [OK]

Hint: Remember: session_start() must run before any output [OK]

Common Mistakes:

• Thinking session_start() ends a session
• Confusing sessions with database connections
• Calling session_start() after HTML output

2. Which of the following is the correct way to start a session in PHP?

easy

A. session.begin();

B. start_session();

C. session_start();

D. begin_session();

Solution

1. Step 1: Recall PHP session function syntax

   The correct function to start a session is session_start() with an underscore and parentheses.

2. Step 2: Check other options for syntax errors

   Options B, C, and D are not valid PHP functions and will cause errors.

3. Final Answer:

   session_start(); -> Option C

4. Quick Check:

   Correct PHP session start syntax = A [OK]

Hint: Use exact function name: session_start() [OK]

Common Mistakes:

• Using wrong function names like start_session()
• Missing parentheses after session_start
• Using camelCase instead of underscore

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

<?php
session_start();
$_SESSION['user'] = 'Alice';
echo $_SESSION['user'];
?>

medium

A. user

B. Alice

C. Array

D. Undefined index error

Solution

1. Step 1: Start session and assign value

   The code starts a session and sets the session variable 'user' to 'Alice'.

2. Step 2: Output the session variable

   Using echo $_SESSION['user']; prints the value stored, which is 'Alice'.

3. Final Answer:

   Alice -> Option B

4. Quick Check:

   $_SESSION['user'] = 'Alice' outputs Alice [OK]

Hint: Session variables store values like arrays [OK]

Common Mistakes:

• Expecting 'user' instead of its value
• Forgetting to call session_start() first
• Confusing session variables with regular variables

4. Identify the error in this PHP code snippet:

<?php
$_SESSION['count'] = 1;
echo $_SESSION['count'];
?>

medium

A. Cannot echo session variables

B. Incorrect variable name $_SESSION

C. Session variables must be integers only

D. Missing session_start() before using $_SESSION

Solution

1. Step 1: Check session initialization

   The code uses $_SESSION but never calls session_start() to begin the session.

2. Step 2: Understand session usage rules

   Without calling session_start(), PHP does not know which session to use, causing errors or empty values.

3. Final Answer:

   Missing session_start() before using $_SESSION -> Option D

4. Quick Check:

   Always call session_start() before $_SESSION [OK]

Hint: Always start session before accessing $_SESSION [OK]

Common Mistakes:

• Using $_SESSION without session_start()
• Assuming $_SESSION works like normal variables
• Trying to echo $_SESSION without initialization

5. You want to count how many times a user visits a page using sessions. Which code correctly increments the visit count each time the page loads?

<?php
// Fill in the missing part

if (isset($_SESSION['visits'])) {
    $_SESSION['visits']++;
} else {
    $_SESSION['visits'] = 1;
}
echo "Visit number: " . $_SESSION['visits'];
?>

hard

A. session_start();

B. session_destroy();

C. session_unset();

D. session_write_close();

Solution

1. Step 1: Recognize session must be started

   To use $_SESSION variables, the session must be started with session_start(); at the top.

2. Step 2: Understand the code logic

   The code checks if 'visits' exists in the session, increments it if yes, or sets it to 1 if no, then prints the count.

3. Final Answer:

   session_start(); -> Option A

4. Quick Check:

   Start session before using $_SESSION to track visits [OK]

Hint: Always call session_start() before session variables [OK]

Common Mistakes:

• Forgetting session_start() causes no session data
• Using session_destroy() resets visits
• Confusing session_unset() with starting session