Operator precedence and evaluation in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this PHP code with mixed operators?

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

PHP

<?php
$result = 3 + 4 * 2 / (1 - 5) ** 2 ** 3;
echo $result;
?>

A 7

B 11

C 3.0001220703125

D Syntax Error

💡 Hint

Remember that exponentiation (**) is right-associative and has higher precedence than multiplication and division.

The expression evaluates the exponentiation first, then multiplication and division, and finally addition. The result is approximately 3.0001220703125.

❓ Predict Output

intermediate

What is the output of this PHP code with logical and comparison operators?

What will this PHP code print?

PHP

<?php
$a = true;
$b = false;
$c = false;
$result = $a && $b || $c;
echo (int)$result;
?>

A 1

B 0

C Syntax Error

D null

💡 Hint

Logical AND (&&) has higher precedence than logical OR (||).

The expression is evaluated as ($a && $b) || $c, which is (true && false) || false = false || false = false, so output is 0.

🔧 Debug

advanced

What error does this PHP code raise due to operator precedence?

Examine the following PHP code. What error will it produce when run?

PHP

<?php
$value = 5;
if ($value > 3 && $value < 10 || $value = 0) {
    echo 'Valid';
} else {
    echo 'Invalid';
}
?>

A Warning: Assignment inside condition without parentheses

B No error, outputs 'Valid'

C Parse error: syntax error

D Outputs 'Invalid'

💡 Hint

Assignment (=) inside conditions can cause warnings if not grouped properly.

The assignment inside the condition is allowed but triggers a warning because it is ambiguous without parentheses. The expression evaluates with assignment having lower precedence than logical operators.

❓ Predict Output

advanced

What is the output of this PHP code with ternary and concatenation?

What will this PHP code print?

PHP

<?php
$score = 85;
$message = 'Result: ' . $score > 80 ? 'Pass' : 'Fail';
echo $message;
?>

A Pass

B Result: Pass

C Fail

D Result: 1

💡 Hint

Concatenation (.) has lower precedence than comparison (>) and ternary (?:).

The expression is parsed as ('Result: ' . $score) > 80 ? 'Pass' : 'Fail'. The concatenation results in a string, which when compared to 80 converts to 0, so 0 > 80 is false, so 'Fail' is chosen. But echo prints the boolean result of the comparison concatenation, which is 1 (true) or empty string (false). Actually, operator precedence causes unexpected behavior here, resulting in 'Result: 1'.

❓ Predict Output

expert

What is the value of $x after this PHP code runs?

Analyze this PHP code and determine the final value of $x.

PHP

<?php
$x = 2;
$x *= $x + 3;
echo $x;
?>

A 10

B 25

C 7

D Syntax Error

💡 Hint

Remember that the right side of the *= operator is evaluated before multiplication.

The expression is evaluated as $x = $x * ($x + 3) = 2 * (2 + 3) = 2 * 5 = 10.