Session variables 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 session variables. What will be printed?

PHP

<?php
session_start();
$_SESSION['count'] = 1;
$_SESSION['count'] += 1;
echo $_SESSION['count'];
?>

A 2

B 1

C 3

D Undefined index error

💡 Hint

Remember that session variables keep their values during the session and you can update them like normal variables.

The session variable 'count' is first set to 1, then incremented by 1, so the output is 2.

❓ Predict Output

intermediate

What error does this PHP session code produce?

What error will this PHP code produce when run?

PHP

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

A Warning: session_start() not called

B No error, outputs 'Alice'

C Fatal error: Undefined variable 'SESSION'

D Parse error: syntax error

💡 Hint

Session variables require a special function to be called before using them.

Without session_start(), PHP produces a warning that the session has not been started. Accessing $_SESSION without starting the session is not recommended and may cause warnings or unexpected behavior.

🔧 Debug

advanced

Why does this PHP session code not keep the value?

This PHP code tries to count page visits using a session variable but always prints 1. Why?

PHP

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

A The variable 'visits' is not initialized before use

B The else block resets 'visits' to 1 every time, so it never increments

C PHP sessions are disabled on the server

D session_start() is missing, so session variables don't work

💡 Hint

Look carefully at what happens inside the else block.

The else block sets 'visits' back to 1 every time, so the count never increases beyond 1.

❓ Predict Output

advanced

What is the output of this PHP session code with unset?

What will this PHP code output?

PHP

<?php
session_start();
$_SESSION['name'] = 'Bob';
unset($_SESSION['name']);
echo isset($_SESSION['name']) ? $_SESSION['name'] : 'No name';
?>

A Empty string

B Bob

C Undefined index error

D No name

💡 Hint

What does unset() do to a session variable?

unset() removes the session variable, so isset() returns false and 'No name' is printed.

❓ Predict Output

expert

What is the output of this PHP session code with session_destroy?

What will this PHP code output?

PHP

<?php
session_start();
$_SESSION['color'] = 'red';
session_destroy();
echo isset($_SESSION['color']) ? $_SESSION['color'] : 'No color';
?>

A Warning: session has been destroyed

B No color

C red

D Empty string

💡 Hint

Does session_destroy() immediately clear the $_SESSION array in the current script?

session_destroy() ends the session but does not clear the $_SESSION superglobal in the current script, so 'red' is printed.