Operators · Lesson 1 of 6

Arithmetic Operators

Calculate with addition, subtraction, multiplication, division, and remainder.

Lesson

PHP uses +, -, *, /, and % for common arithmetic. Division by zero is invalid, so guard a divisor when it can come from user input. Parentheses make the intended order clear, especially when a calculation mixes multiplication and addition. The remainder operator is useful for recurring patterns such as checking whether a number is even. Further guidance Evaluate an expression from its grouped parts and add parentheses whenever precedence is not obvious. Check divisors before division, be cautious with floating-point equality, and avoid changing state inside a complicated expression. Small, named intermediate values make calculations easier to verify. Practice task: Create a fresh example for Arithmetic Operators. Predict the result before running it, then change one input and explain why the result changes. Test a normal case and one boundary or invalid case where it applies. Compare your output with the example and note one rule you would use in a real project.

Code examples

PHP

$price = 12;
$quantity = 3;
$total = $price * $quantity;
echo $total, ' ', ($quantity % 2 === 1 ? 'odd count' : 'even count');

Expected output

36 odd count

Key points

Calculate with addition, subtraction, multiplication, division, and remainder.
Make calculation order explicit with parentheses and named intermediate values.
Check edge cases such as zero divisors and floating-point precision.

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