Arithmetic operators in PHP - Mini Project: Build & Apply

Arithmetic Operators in PHP

📖 Scenario: You are helping a small shop owner calculate prices and discounts using simple math.

🎯 Goal: Build a PHP script that uses arithmetic operators to calculate total price, discount, and final price.

📋 What You'll Learn

Create variables with exact values

Use arithmetic operators: +, -, *, /

Print the final calculated result

💡 Why This Matters

🌍 Real World

Calculating prices, discounts, and totals is common in shopping and billing systems.

💼 Career

Understanding arithmetic operators is essential for backend programming, especially in e-commerce and finance applications.

1

Create initial price variables

Create two variables called $price1 and $price2 with values 100 and 50 respectively.

PHP

<?php

// Create variables $price1 and $price2 with values 100 and 50
// Your code here

Hint

Use the = operator to assign values to variables.

2

Add a discount percentage variable

Create a variable called $discountPercent and set it to 10.

PHP

<?php

$price1 = 100;
$price2 = 50;

// Create variable $discountPercent with value 10
// Your code here

Hint

Remember to end each statement with a semicolon.

3

Calculate total price and discount amount

Create a variable $totalPrice that adds $price1 and $price2. Then create a variable $discountAmount that calculates $totalPrice times $discountPercent divided by 100.

PHP

<?php

$price1 = 100;
$price2 = 50;
$discountPercent = 10;

// Calculate $totalPrice as sum of $price1 and $price2
// Calculate $discountAmount as $totalPrice * $discountPercent / 100
// Your code here

Hint

Use + to add and * and / for multiplication and division.

4

Calculate final price and print it

Create a variable $finalPrice that subtracts $discountAmount from $totalPrice. Then print the text "Final price: " followed by the value of $finalPrice.

PHP

<?php

$price1 = 100;
$price2 = 50;
$discountPercent = 10;

$totalPrice = $price1 + $price2;
$discountAmount = $totalPrice * $discountPercent / 100;

// Calculate $finalPrice as $totalPrice - $discountAmount
// Print "Final price: " and $finalPrice
// Your code here

Hint

Use - to subtract and print() to show output.

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