Boolean type behavior in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Boolean evaluation of different values

What is the output of this PHP code snippet?

PHP

<?php
$values = [0, 1, -1, "0", "false", "", null, [], [0]];
foreach ($values as $v) {
    echo (bool)$v ? 'true ' : 'false ';
}
?>

A false true true true false false false false true

B false true false false false false false false true

C false true true false false false false false true

D false true true false true false false false true

💡 Hint

Remember how PHP treats strings and arrays when cast to boolean.

In PHP, the following values are considered false when cast to boolean: 0, "0", empty string "", null, and empty array []. All other values are true.

So the outputs correspond to these evaluations.

❓ Predict Output

intermediate

Boolean comparison with loose equality

What is the output of this PHP code?

PHP

<?php
var_dump(false == 0);
var_dump(false == '');
var_dump(false == null);
var_dump(false == 'false');
?>

A bool(true) bool(true) bool(true) bool(false)

B bool(false) bool(true) bool(true) bool(false)

C bool(true) bool(false) bool(true) bool(false)

D bool(true) bool(true) bool(false) bool(false)

💡 Hint

Loose equality in PHP converts types before comparing.

In PHP, false == 0, false == '', and false == null all evaluate to true because of type juggling. However, false == 'false' is false because 'false' is a non-empty string and converts to true in boolean context.

🔧 Debug

advanced

Unexpected boolean result in conditional

Why does this PHP code always print "No" even when $value is 1?

PHP

<?php
$value = 1;
if ($value == true) {
    echo "Yes";
} else {
    echo "No";
}
?>

A Because the code is correct and it should print "Yes", so the problem is elsewhere

B Because the variable $value is an integer and cannot be compared to boolean

C Because the code uses == instead of ===, causing unexpected type coercion

D Because == compares values loosely and 1 is not equal to true

💡 Hint

Test the code by running it and see what it prints.

The code actually prints "Yes" because 1 == true evaluates to true in PHP. So the problem is not in this snippet.

📝 Syntax

advanced

Boolean expression syntax error

Which option will cause a syntax error in PHP?

A if ($a && $b) { echo 'Yes'; }

B if ($a &&) { echo 'Yes'; }

C if ($a & $b) { echo 'Yes'; }

D if ($a and $b) { echo 'Yes'; }

💡 Hint

Look for incomplete boolean expressions.

Option B has a syntax error because the && operator is missing the right operand.

🚀 Application

expert

Count how many values are true in mixed array

Given this PHP array, how many elements evaluate to true when cast to boolean?

PHP

<?php
$items = [0, "", "0", null, false, true, 1, -1, [], [0], "false"];
$count = 0;
foreach ($items as $item) {
    if ((bool)$item) {
        $count++;
    }
}
echo $count;
?>

A 8

B 7

C 5

D 6

💡 Hint

Recall which values PHP treats as false.

False values are: 0, "", "0", null, false, and empty array []. All others are true.

Counting true values: true, 1, -1, [0], "false" → 5