Arithmetic operators in PHP

Introduction

Arithmetic operators help you do math with numbers in your program. They let you add, subtract, multiply, and divide values easily.

Calculating the total price of items in a shopping cart.

Finding the difference between two dates or times.

Increasing a score in a game after a player earns points.

Splitting a bill evenly among friends.

Converting units, like inches to centimeters.

Syntax

PHP

$result = $a + $b;
$result = $a - $b;
$result = $a * $b;
$result = $a / $b;
$result = $a % $b;

Use + for addition, - for subtraction, * for multiplication, / for division, and % for remainder (modulus).

Make sure variables hold numbers before using arithmetic operators.

Examples

Adds 5 and 3, then prints 8.

PHP

$sum = 5 + 3;
echo $sum;

Subtracts 4 from 10, then prints 6.

PHP

$difference = 10 - 4;
echo $difference;

Multiplies 7 by 6, then prints 42.

PHP

$product = 7 * 6;
echo $product;

Finds remainder when 10 is divided by 3, then prints 1.

PHP

$remainder = 10 % 3;
echo $remainder;

Sample Program

This program shows all basic arithmetic operations between 15 and 4, printing each result on a new line.

PHP

<?php
$a = 15;
$b = 4;

echo "Addition: " . ($a + $b) . "\n";
echo "Subtraction: " . ($a - $b) . "\n";
echo "Multiplication: " . ($a * $b) . "\n";
echo "Division: " . ($a / $b) . "\n";
echo "Modulus: " . ($a % $b) . "\n";
?>

Important Notes

Division by zero will cause an error, so avoid dividing by zero.

Modulus operator (%) gives the remainder after division, useful for checking even/odd numbers.

Summary

Arithmetic operators let you do basic math in PHP.

Use +, -, *, /, and % for addition, subtraction, multiplication, division, and remainder.

Always check your numbers to avoid errors like dividing by zero.

Practice

1. Which arithmetic operator in PHP is used to find the remainder of a division?

easy

A. The subtraction operator (-)

B. The modulus operator (%)

C. The multiplication operator (*)

D. The division operator (/)

Solution

1. Step 1: Understand the modulus operator and compare with other operators

   The modulus operator (%) returns the remainder after division of two numbers. Division (/) returns the quotient, multiplication (*) multiplies, and subtraction (-) subtracts.

2. Final Answer:

   The modulus operator (%) -> Option B

3. Quick Check:

   Remainder = % [OK]

Hint: Remainder means modulus (%) operator [OK]

Common Mistakes:

• Confusing division (/) with modulus (%)
• Using multiplication (*) instead of modulus
• Thinking subtraction (-) gives remainder

2. Which of the following is the correct syntax to add two variables $a and $b in PHP?

easy

A. $sum = $a / $b;

B. $sum = $a - $b;

C. $sum = $a * $b;

D. $sum = $a + $b;

Solution

1. Step 1: Identify the addition operator and check the syntax correctness

   In PHP, the plus sign (+) adds two numbers or variables. The syntax $sum = $a + $b; correctly assigns the sum of $a and $b to $sum.

2. Final Answer:

   $sum = $a + $b; -> Option D

3. Quick Check:

   Addition uses + [OK]

Hint: Use + for addition between variables [OK]

Common Mistakes:

• Using - instead of + for addition
• Using * or / which are multiplication/division
• Missing semicolon at end

3. What will be the output of the following PHP code?

$x = 10;
$y = 3;
echo $x % $y;

medium

A. 1

B. 3

C. 0

D. Syntax Error

Solution

1. Step 1: Calculate the modulus of 10 and 3 and understand the output of echo $x % $y;

   10 divided by 3 is 3 with a remainder of 1. The modulus operator (%) returns the remainder, so output is 1.

2. Final Answer:

   1 -> Option A

3. Quick Check:

   10 % 3 = 1 [OK]

Hint: Modulus gives remainder, 10 % 3 = 1 [OK]

Common Mistakes:

• Confusing modulus with division result
• Expecting 3 instead of remainder 1
• Syntax errors from missing semicolon

4. Identify the error in this PHP code snippet:

$a = 5;
$b = 0;
echo $a / $b;

medium

A. Incorrect use of multiplication operator

B. Syntax error due to missing semicolon

C. Division by zero error

D. No error, outputs 0

Solution

1. Step 1: Analyze the division operation and check for syntax correctness

   Dividing any number by zero is not allowed and causes an error in PHP. Semicolons are present; multiplication operator is not used here.

2. Final Answer:

   Division by zero error -> Option C

3. Quick Check:

   Division by zero causes error [OK]

Hint: Never divide by zero to avoid errors [OK]

Common Mistakes:

• Ignoring division by zero error
• Thinking output is 0
• Confusing syntax error with runtime error

5. You want to calculate the total cost after applying a 15% discount on a price stored in $price. Which PHP expression correctly calculates the discounted price?

hard

A. $discounted = $price - ($price * 0.15);

B. $discounted = $price + ($price * 0.15);

C. $discounted = $price * 0.15;

D. $discounted = $price / 0.15;

Solution

1. Step 1: Calculate the discount amount and subtract discount from original price

   Multiply the price by 0.15 to get 15% of the price. Subtract the discount amount from the original price to get the discounted price.

2. Final Answer:

   $discounted = $price - ($price * 0.15); -> Option A

3. Quick Check:

   Discounted price = price - 15% price [OK]

Hint: Subtract 15% of price for discount [OK]

Common Mistakes:

• Adding discount instead of subtracting
• Using only 15% value without subtracting
• Dividing price by 0.15 incorrectly