Starting and using sessions in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP session code?

Consider the following PHP code that uses sessions. What will be printed when this script runs?

PHP

<?php
session_start();
if (!isset($_SESSION['count'])) {
    $_SESSION['count'] = 1;
} else {
    $_SESSION['count']++;
}
echo $_SESSION['count'];
?>

A 1

B 0

C 2

D Undefined index error

💡 Hint

Think about what happens the first time the session variable is set.

The session variable 'count' is not set initially, so it is set to 1 and then printed. The output is 1.

❓ Predict Output

intermediate

What will this PHP code output after two page loads?

This PHP script uses sessions to count visits. What will it output on the second page load?

PHP

<?php
session_start();
if (!isset($_SESSION['visits'])) {
    $_SESSION['visits'] = 0;
}
$_SESSION['visits'] += 1;
echo $_SESSION['visits'];
?>

A 1

B 0

C Error: session not started

D 2

💡 Hint

Remember the session variable keeps its value between page loads.

On the first load, visits is set to 0 then incremented to 1. On the second load, it increments from 1 to 2, so output is 2.

🔧 Debug

advanced

Why does this PHP session code cause a warning?

Look at this PHP code snippet. It causes a warning about headers already sent. Why?

PHP

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

A The session variable 'user' is not initialized

B session_start() is deprecated after echo

C session_start() must be called before any output is sent

D You cannot set session variables after echo

💡 Hint

Think about when PHP sends HTTP headers.

session_start() sends HTTP headers. Headers must be sent before any output like echo. Here echo sends output first, causing the warning.

📝 Syntax

advanced

Which option correctly starts a session and sets a variable?

Choose the correct PHP code that starts a session and sets the session variable 'role' to 'admin'.

A

<?php
start_session();
$_SESSION['role'] = 'admin';
?>

B

<?php
session_start();
$_SESSION['role'] = 'admin';
?>

C

<?php
session_start;
$_SESSION['role'] = 'admin';
?>

D

<?php
session_start();
session['role'] = 'admin';
?>

💡 Hint

Check the function name and syntax carefully.

Only option B correctly calls session_start() as a function and uses $_SESSION superglobal properly.

🚀 Application

expert

What is the value of $_SESSION['total'] after this code runs?

Given this PHP code, what will be the value of $_SESSION['total'] after execution?

PHP

<?php
session_start();
if (!isset($_SESSION['total'])) {
    $_SESSION['total'] = 5;
}
function addToTotal($value) {
    $_SESSION['total'] += $value;
}
addToTotal(10);
addToTotal(-3);
?>

A 12

B 15

C 5

D Error: Undefined index 'total'

💡 Hint

Calculate the additions step by step.

Initially total is 5. Then addToTotal(10) makes it 15. Then addToTotal(-3) reduces it to 12.

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