Nested loop execution in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested for loops with break

What is the output of this PHP code?

PHP

<?php
for ($i = 1; $i <= 3; $i++) {
    for ($j = 1; $j <= 3; $j++) {
        if ($j == 2) {
            break;
        }
        echo "$i$j ";
    }
}
?>

A 12 22 32

B 11 12 21 22 31 32

C 11 12 13 21 22 23 31 32 33

D 11 21 31

💡 Hint

Remember that break exits the inner loop immediately when condition is met.

The inner loop breaks when $j == 2, so only $j == 1 is printed for each $i. So output is 11 21 31.

❓ Predict Output

intermediate

Output of nested while loops with continue

What is the output of this PHP code?

PHP

<?php
$i = 1;
while ($i <= 2) {
    $j = 1;
    while ($j <= 3) {
        if ($j == 2) {
            $j++;
            continue;
        }
        echo "$i$j ";
        $j++;
    }
    $i++;
}
?>

A 11 13 12 21 23 22

B 11 13 21 23

C 11 12 13 21 22 23

D 12 22

💡 Hint

The continue skips printing when $j == 2 but increments $j before continuing.

When $j == 2, it increments $j and continues, skipping echo. So 12 and 22 are skipped.

🧠 Conceptual

advanced

Number of iterations in nested loops

How many times will the innermost statement execute in this PHP code?

PHP

<?php
for ($a = 0; $a < 4; $a++) {
    for ($b = 0; $b < 3; $b++) {
        for ($c = 0; $c < 2; $c++) {
            // innermost statement
        }
    }
}
?>

A 24

B 9

C 12

D 6

💡 Hint

Multiply the number of iterations of each loop.

4 * 3 * 2 = 24 times the innermost statement runs.

🔧 Debug

advanced

Identify the error in nested loops

What error will this PHP code produce?

PHP

<?php
for ($x = 0; $x < 3; $x++) {
    for ($y = 0; $y < 3; $y++)
        echo "$x$y ";
}
?>

A No error, outputs '000102...222'

B Parse error: syntax error, unexpected '}'

C Fatal error: Maximum execution time exceeded

D Warning: Undefined variable

💡 Hint

Check the braces carefully for matching pairs.

The inner for loop lacks braces but the closing brace after echo is extra, causing syntax error.

🚀 Application

expert

Output of nested loops with conditional break and continue

What is the output of this PHP code?

PHP

<?php
for ($i = 1; $i <= 3; $i++) {
    for ($j = 1; $j <= 3; $j++) {
        if ($i == $j) {
            continue;
        }
        if ($j == 3) {
            break;
        }
        echo "$i$j ";
    }
}
?>

A 12 13 21 31 32

B 12 21 23 31 32

C 12 21 31 32

D 12 13 21 23 31

💡 Hint

Remember continue skips current iteration, break exits inner loop.

When $i == $j, continue skips printing. When $j == 3, break exits inner loop. The output is 12 21 31 32.