While loop execution model in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP while loop?

Consider the following PHP code snippet. What will it print?

PHP

<?php
$i = 3;
while ($i > 0) {
    echo $i . " ";
    $i--;
}
?>

A 3 2 1

B 1 2 3

C 3 2 1 0

D 0 1 2 3

💡 Hint

Remember the loop runs while the condition is true and $i decreases each time.

The loop starts with $i = 3 and prints it. Then $i decreases by 1 each iteration until $i is 0, which stops the loop. So it prints '3 2 1 '.

❓ Predict Output

intermediate

How many times does this while loop run?

Look at this PHP code. How many times will the loop body execute?

PHP

<?php
$count = 0;
$num = 5;
while ($num > 2) {
    $count++;
    $num--;
}
echo $count;

A 5

B 4

C 3

D 2

💡 Hint

Count how many times $num is greater than 2 before the loop stops.

The loop runs while $num is 5,4,3 (3 times). When $num becomes 2, the condition fails and loop stops. So $count is 3.

🔧 Debug

advanced

Identify the error in this while loop code

This PHP code is supposed to print numbers 1 to 5 but causes an error or unexpected behavior. What is the problem?

PHP

<?php
$i = 1;
while ($i <= 5)
    echo $i . " ";
    $i++;
?>

A Variable $i is not initialized before the loop

B The condition uses <= instead of <, causing an off-by-one error

C Missing semicolon after echo statement

D The increment $i++ is outside the loop block, causing an infinite loop

💡 Hint

Check which statements are inside the loop and which are not.

Without braces, only the first statement after while is inside the loop. The $i++ runs once after loop ends, so $i never changes inside loop, causing infinite loop.

🧠 Conceptual

advanced

What happens if the while loop condition is false initially?

Consider this PHP code snippet. What will be the output?

PHP

<?php
$x = 0;
while ($x > 0) {
    echo "Looping ";
    $x--;
}
echo "Done";

A Prints only 'Done'

B Prints 'Looping ' multiple times then 'Done'

C Prints nothing

D Causes an infinite loop

💡 Hint

Think about whether the loop body runs if the condition is false at start.

Since $x is 0 and condition $x > 0 is false initially, the loop body never runs. Only 'Done' is printed.

❓ Predict Output

expert

What is the final value of $result after this while loop?

Analyze the PHP code below and find the value of $result after the loop finishes.

PHP

<?php
$n = 4;
$result = 1;
while ($n > 0) {
    $result *= $n;
    $n--;
}
echo $result;

A 10

B 24

C 0

D 1

💡 Hint

This loop multiplies $result by $n each time, decreasing $n from 4 to 1.

The loop calculates 4 * 3 * 2 * 1 = 24, so $result is 24 after the loop.