Assignment and compound assignment in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of compound assignment with strings

What is the output of this PHP code?

PHP

<?php
$a = "Hello";
$a .= " World";
echo $a;
?>

A World

B HelloWorld

C Hello

D Hello World

💡 Hint

The .= operator adds the right string to the left string.

The .= operator appends the right string to the left string variable. So $a becomes "Hello World".

❓ Predict Output

intermediate

Result of compound assignment with numbers

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

PHP

<?php
$x = 10;
$x *= 3 + 2;
echo $x;
?>

A 50

B 15

C 60

D 30

💡 Hint

Remember operator precedence: multiplication and addition.

The expression $x *= 3 + 2 is evaluated as $x *= (3 + 2) = $x *= 5, so $x becomes 10 * 5 = 50.

❓ Predict Output

advanced

Output of chained compound assignments

What is the output of this PHP code?

PHP

<?php
$a = 5;
$b = 10;
$c = 15;
$a += $b -= $c;
echo "$a $b $c";
?>

A 0 -5 15

B 20 -5 15

C 20 25 15

D 5 10 15

💡 Hint

Evaluate inner assignment first, then outer.

First $b -= $c means $b = 10 - 15 = -5. Then $a += $b means $a = 5 + (-5) = 0. $c stays 15.

❓ Predict Output

advanced

Effect of compound assignment with arrays

What error or output does this PHP code produce?

PHP

<?php
$arr = [1, 2, 3];
$arr += [4, 5];
print_r($arr);
?>

A Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 )

B Array ( [0] => 1 [1] => 2 [2] => 3 )

C Fatal error: Unsupported operand types

D Array ( [0] => 1 [1] => 2 [2] => 3 [4] => 5 )

💡 Hint

The += operator for arrays adds elements with keys that do not exist in the left array.

The += operator adds elements from the right array only if the key does not exist in the left array. The right array [4, 5] has keys 0=>4 and 1=>5, both exist in the left array, so nothing is added.

❓ Predict Output

expert

Final value after mixed compound assignments

What is the final value of $result after running this PHP code?

PHP

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

A 3

B 5

C 4

D 6

💡 Hint

Calculate step by step following the order of operations.

Step 1: $result = 2 Step 2: $result *= 3 → 6 Step 3: $result += 4 → 10 Step 4: $result /= 2 → 5 Step 5: $result -= 1 → 4 Output is 4.