How to Find Area of a Circle with Diameter in PHP | Functions

How to find area of a circle with diameter in PHP using functions.

In this article, you will learn how to find area of a circle with diameter in PHP using functions.

Example

You should have knowledge of the following topics in PHP programming to understand this program:

• PHP echo and print statement

1. By using the default value of PI = 3.14

<?php
$r = 12; $d = NULL; $c = NULL; $a = NULL;
// $r = radius, $d = diameter, $c = circumference, $a = area

// It will calculate the diameter, circumference, and area
$d = 2 * $r;
$c = 2 * 3.14 * $r;
$a = 3.14 * ($r * $r);

echo "\nDiameter       = " . $d . " units";
echo "\nCircumference  = " . $c . " units";
echo "\nArea           = " . $a . " sq. units";
?>

Run

Output

Explanation

In the above program, we have set the input variable $r with the value 12. Then we applied the standard formula to calculate the diameter, circumference, and area.

Standard formulas are given at the top of the article near the example portion can see there.

After the whole calculation, It will return these values following: 

• Diameter = 24 units
• Circumference = 75.36 units
• Area = 452.16 sq. units

2. By using the pi() function

<?php
$r = 12; $d = NULL; $c = NULL; $a = NULL;
// $r = radius, $d = diameter, $c = circumference, $a = area

// It will calculate the diameter, circumference, and area
$d = 2 * $r;
$c = 2 * pi() * $r;
$a = pi() * pow($r, 2);

echo "\nDiameter       = " . $d . " units";
echo "\nCircumference  = " . $c . " units";
echo "\nArea           = " . $a . " sq. units";
?>

Run

Output

How to Find Area of a Circle with Diameter in PHP using Functions

<?php
// To calculate the diameter
function diameter($r) {
    return 2 * $r;
}

// To calculate the circumference
function circumference($r) {
    return 2 * 3.14 * $r;
}

// To calculate the area
function area($r) {
    return 3.14 * ($r * $r);
}

$r = 12; // $r = radius

echo "\nDiameter       = " . diameter($r) . " units";
echo "\nCircumference  = " . circumference($r) . " units";
echo "\nArea           = " . area($r) . " sq. units";
?>

Run