Example 3: Basic Calculator

Math operators and calculations in PHP

Download file calculadora

🎯 Live Demo

Operation results:

Addition
15 + 5 = 20
Subtraction
15 - 5 = 10
Multiplication
15 × 5 = 75
Division
15 ÷ 5 = 3

Change the numbers!

Quick numbers:

📖 Code Explanation

Complete PHP Code

<?php
$numero1 = 15;
$numero2 = 5;

$suma = $numero1 + $numero2;
$resta = $numero1 - $numero2;
$multiplicacion = $numero1 * $numero2;
$division = $numero1 / $numero2;

echo "La suma es: $suma";
echo "La resta es: $resta"; 
echo "La multiplicación es: $multiplicacion";
echo "La división es: $division";
?>

📝 Lines 1-2: Numeric variable declaration

$numero1 = 15;
$numero2 = 5;

What does it do? Creates two numeric variables that will serve as operands for the operations.

Why is it done this way? In PHP, numbers are assigned directly without quotes. PHP automatically detects that they are numbers.

💡 Concept: Numeric types

PHP has two main types of numbers:
Integer: Whole numbers (15, -3, 0)
Float: Decimal numbers (3.14, -2.5, 0.0)

📝 Lines 4-7: Math operations

$suma = $numero1 + $numero2;
$resta = $numero1 - $numero2;
$multiplicacion = $numero1 * $numero2;
$division = $numero1 / $numero2;

What does it do? Performs the four basic math operations and stores the results in variables.

Why is it done this way? Each operation uses a specific math operator and stores the result for later use.

💡 Concept: Arithmetic operators

+ Addition
- Subtraction
* Multiplication
/ Division
% Modulo (division remainder)

📝 Lines 9-12: Display results

echo "La suma es: $suma";
echo "La resta es: $resta";
echo "La multiplicación es: $multiplicacion";
echo "La división es: $division";

What does it do? Displays each result with a descriptive message.

Why is it done this way? Uses variable interpolation to create clear messages that include both the text and the calculated results.

💡 Concept: Operator precedence

PHP follows standard math rules:
1. Parentheses ()
2. Multiplication and division (* /)
3. Addition and subtraction (+ -)

🔢 Math Operators in PHP

+

Addition

Adds two values

$resultado = 5 + 3; // 8
-

Subtraction

Subtracts the second value from the first

$resultado = 5 - 3; // 2
*

Multiplication

Multiplies two values

$resultado = 5 * 3; // 15
/

Division

Divides the first value by the second

$resultado = 6 / 3; // 2
%

Modulo

Returns the remainder of a division

$resultado = 5 % 3; // 2
**

Exponentiation

Raises a number to a power

$resultado = 2 ** 3; // 8

🎯 Key Concepts Learned

Numeric Variables

  • Assigned without quotes
  • PHP automatically detects the type
  • Can be integers or floats
  • Operations can be performed directly

Arithmetic Operators

  • Special symbols for operations
  • Follow math precedence
  • Can use variables and numbers
  • Return a result

Error Handling

  • Division by zero causes an error
  • Use conditionals to prevent it
  • Validate data before operating
  • Show clear error messages

💪 Practical Exercise

Extend the calculator

Practice these changes to improve your skills:

  1. Add the modulo operation (%) to the calculator
  2. Implement exponentiation (**) to calculate powers
  3. Create an operation that calculates the average of 3 numbers
  4. Add validation to prevent division by zero
  5. Calculate the area of a circle (π × radio²)

Solution 1: Modulo

<?php
$modulo = $numero1 % $numero2;
echo "El módulo es: $modulo";
?>

Solution 2: Exponentiation

<?php
$potencia = $numero1 ** $numero2;
echo "La potencia es: $potencia";
?>

Solution 3: Average

<?php
$numero3 = 10;
$promedio = ($numero1 + $numero2 + $numero3) / 3;
echo "El promedio es: $promedio";
?>

Solution 4: Division validation

<?php
if ($numero2 != 0) {
    $division = $numero1 / $numero2;
    echo "La división es: $division";
} else {
    echo "Error: No se puede dividir por cero";
}
?>

Solution 5: Area of the circle

<?php
$radio = 5;
$area = pi() * ($radio ** 2);
echo "El área del círculo es: " . round($area, 2);
?>