Arithmetic operators in PHP - Step-by-Step Execution

Concept Flow - Arithmetic operators

Start

↓

Read operands

↓

Choose operator (+, -, *, /, %)

↓

Perform calculation

↓

Store/Display result

↓

End

This flow shows how PHP reads two numbers, applies an arithmetic operator, calculates the result, and then outputs it.

Execution Sample

PHP

<?php
$a = 10;
$b = 3;
$result = $a + $b;
echo $result;
?>

This code adds two numbers and prints the result.

Execution Table

Step	Variable	Value	Operation	Result/Output
1	$a	10	Assign 10	10
2	$b	3	Assign 3	3
3	$result	10 + 3	Add $a and $b	13
4	echo $result	13	Print result	13 printed
5	End	-	-	Program ends

💡 Program ends after printing the result.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
$a	undefined	10	10	10	10
$b	undefined	undefined	3	3	3
$result	undefined	undefined	undefined	13	13

Key Moments - 2 Insights

Why does $result hold 13 after step 3?

Because $result is assigned the sum of $a and $b, which are 10 and 3 respectively, as shown in execution_table row 3.

What happens if we try to echo $result before assigning it?

It would cause an error or print nothing because $result is undefined before step 3, as seen in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of $b after step 2?

A undefined

B 3

C 10

D 13

💡 Hint

Check the 'Value' column for $b at step 2 in the execution_table.

At which step is the addition operation performed?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'Operation' column mentioning addition in the execution_table.

If $a was changed to 7, what would $result be after step 3?

A 7

B 3

C 10

D 11

E 9

💡 Hint

Recall $result is $a + $b; changing $a to 7 means $result = 7 + 3.

Concept Snapshot

PHP Arithmetic Operators:
- Use +, -, *, /, % to do math.
- Variables hold numbers.
- Example: $result = $a + $b;
- Result can be printed with echo.
- Operators work left to right.

Full Transcript

This example shows how PHP uses arithmetic operators. First, variables $a and $b get values 10 and 3. Then $result adds them with +. Finally, echo prints 13. The flow is: assign values, calculate, print, end. Variables change step by step. Beginners often wonder why $result is 13 or what happens if $result is used before assignment. The quiz checks understanding of variable values and operation steps.

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