Arithmetic operators in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the '+' operator do in PHP?

The '+' operator adds two numbers together. For example, 3 + 2 equals 5.

beginner

What is the result of 10 - 4 in PHP?

The result is 6 because the '-' operator subtracts the right number from the left number.

beginner

How does the '*' operator work in PHP?

The '*' operator multiplies two numbers. For example, 5 * 3 equals 15.

beginner

What does the '/' operator do in PHP?

The '/' operator divides the left number by the right number. For example, 10 / 2 equals 5.

beginner

What is the '%' operator used for in PHP?

The '%' operator finds the remainder after division of one number by another. For example, 7 % 3 equals 1.

What is the result of 8 + 2 * 3 in PHP?

A 24

B 30

C 18

D 14

Multiplication (*) has higher priority than addition (+), so 2 * 3 = 6, then 8 + 6 = 14.

Which operator gives the remainder of a division in PHP?

A %

B +

C *

D -

The '%' operator returns the remainder after division.

What is the output of 15 / 4 in PHP?

A 3

B 3.75

C 4

D 1

Division (/) returns a float if the division is not exact.

What does the expression 5 - 10 evaluate to in PHP?

A 5

B 15

C -5

D 10

Subtracting a larger number from a smaller one results in a negative number.

Which operator has the highest precedence in PHP among these?

A *

B -

C +

D %

Multiplication (*) and modulus (%) have higher precedence than addition (+) and subtraction (-).

Explain how the basic arithmetic operators work in PHP and give an example for each.

Think about how you do math with numbers and how PHP uses symbols for these.

Describe the order of operations when using multiple arithmetic operators in a PHP expression.

Remember the math rule PEMDAS or BODMAS.

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