Variable scope in functions in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable inside and outside function

What is the output of this PHP code?

PHP

<?php
$a = 5;
function test() {
    $a = 10;
    echo $a;
}
test();
echo $a;

A 105

B 55

C 1010

D 510

💡 Hint

Remember that variables inside functions have their own scope unless declared global.

The function test() has its own local variable $a set to 10, which it prints. Outside the function, $a is 5, so the output is 10 then 5, combined as 105.

❓ Predict Output

intermediate

Using global keyword inside function

What will this PHP code output?

PHP

<?php
$x = 3;
function add() {
    global $x;
    $x += 2;
    echo $x;
}
add();
echo $x;

A 55

B 53

C 35

D 33

💡 Hint

The global keyword lets the function access the variable outside its scope.

The function modifies the global $x by adding 2, so inside the function it prints 5. After the function call, $x remains 5, so the final output is 55.

🔧 Debug

advanced

Why does this code cause an error?

Why does this PHP code cause an error?

PHP

<?php
function foo() {
    echo $y;
}
$y = 7;
foo();

A Because $y is defined after the function call

B Because $y is a reserved keyword in PHP

C Because variables cannot be echoed inside functions

D Because $y is not defined inside the function scope

💡 Hint

Think about where variables are visible inside and outside functions.

The variable $y is defined outside the function and is not global inside foo(). Without global $y; inside the function, $y is undefined there, causing an error.

❓ Predict Output

advanced

Static variable behavior in function

What is the output of this PHP code?

PHP

<?php
function counter() {
    static $count = 0;
    $count++;
    echo $count . ' ';
}
counter();
counter();
counter();

A 0 1 2

B 1 2 3

C 1 1 1

D 3 3 3

💡 Hint

Static variables keep their value between function calls.

The static variable $count starts at 0 and increments each time counter() is called. The outputs are 1, then 2, then 3, printed with spaces.

🧠 Conceptual

expert

Effect of variable scope on recursion

Consider this recursive PHP function:

What will be printed?

A Calls: 4

B Calls: 1

C Calls: 3

D Calls: 0

💡 Hint

Count how many times the function runs including the base case.

The function is called three times: for n=3 (calls=1), n=2 (calls=2), and n=1 (calls=3, base case). It prints "Calls: 3" at the base case.