PHP to calculate the area of a circle

// Define the radius of the circle
$radius = 5;

// Calculate the area of the circle using the formula A = πr^2
$area = pi() * $radius ** 2;

// Print the area of the circle
echo "The area of the circle is $area";

How it works:

The code first defines the radius of the circle, which is 5 in this example. Then, it uses the mathematical constant π (pi) and the radius to calculate the area of the circle using the formula A = πr^2. Finally, it prints the calculated area.

How to implement it effectively:

To implement this code effectively, you can use the following tips:

• Use a meaningful variable name for the radius, such as radius or circle_radius.
• Use the pi() function to get the value of π, which is a more accurate approximation than using a constant value like 3.14.
• Use a descriptive variable name for the calculated area, such as circle_area.
• Consider adding input validation to ensure that the radius is a valid number.