Logical operators in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of combined logical operators

What is the output of this PHP code snippet?

PHP

<?php
$a = true;
$b = false;
$c = true;
$result = $a && $b || $c;
echo $result ? 'Yes' : 'No';
?>

A 1

B No

C Yes

D Error

💡 Hint

Remember that && has higher precedence than || in PHP.

The expression evaluates as ($a && $b) || $c, which is (true && false) || true, so false || true equals true, printing 'Yes'.

❓ Predict Output

intermediate

Logical operator precedence difference

What is the output of this PHP code?

PHP

<?php
$a = false;
$b = true;
$c = false;
$result = $a or $b and $c;
echo $result ? 'True' : 'False';
?>

A True

B False

C 1

D 0

💡 Hint

Remember that 'and' and 'or' have lower precedence than '=' in PHP.

The assignment happens before 'or' and 'and'. So $result = $a (false), then 'or $b and $c' is evaluated but does not affect $result. So $result is false.

🔧 Debug

advanced

Identify the error in logical expression

Which option will cause a syntax error in PHP when using logical operators?

A $result = true && || false;

B $result = true and false or true;

C $result = true && false || true;

D $result = (true || false) && true;

💡 Hint

Look for missing operands between operators.

Option A has '&& ||' without a value between them, causing a syntax error.

❓ Predict Output

advanced

Output of mixed logical operators with parentheses

What is the output of this PHP code?

PHP

<?php
$a = false;
$b = true;
$c = true;
$result = ($a or $b) and $c;
echo $result ? 'Pass' : 'Fail';
?>

A 0

B Fail

C 1

D Pass

💡 Hint

Parentheses change the order of evaluation.

Inside parentheses: $a or $b is false or true = true. Then true and $c (true) is true, so output is 'Pass'.

🧠 Conceptual

expert

Understanding operator precedence and assignment

Given the code below, what is the value of $result after execution?

PHP

<?php
$result = false;
$flag = true;
$result = $flag && false or true;
?>

A false

B true

C 1

D null

💡 Hint

Remember that '&&' has higher precedence than 'or', but '=' has higher precedence than 'or'.

The expression is evaluated as ($result = ($flag && false)) or true. So $result = false, then 'or true' is evaluated but does not affect $result. So $result remains false.