Detailed example of how to realize the area of a circle using PHP-PHP Tutorial-php.cn

Detailed example of how to realize the area of a circle using PHP

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Release： 2023-04-11 16:42:01

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Write a program in PHP to calculate the area of a circle

The circle is one of the most famous shapes in geometry. It consists of a set of points of radius r and always at the same distance from its center. Calculating the area of a circle has many useful applications, such as calculating the volume of an object, calculating the area of a circular pond or field, and even when figuring out how computer programs work. In this article, we will write a simple program using PHP to calculate the area of a circle. I will introduce you to the logic of the program, the required variables and how to use PHP to achieve this task.

In order to calculate the area of a circle, we need to use the following formula:
Area=π×r²

Where, π is the proportionality constant of a circle (about 3.14), and r is the circle radius.

It is very simple to implement this formula using PHP. First, we specify a radius variable, then square it, and then multiply it by π to get the area of the circle.

The following is the PHP code:

<?php
 $radius = 5; //圆的半径
 $area = pi() * pow($radius,2); //用半径计算面积
 echo "圆的半径是".$radius."，面积是".$area;
?>

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The output of this program will be:

The radius of the circle is 5 and the area is 78.539816339745

Let’s see Take a look at how this program works.

First, we define the $radius variable and set it to 5. In this example, we will assume that the radius of our circle is 5. Then, we used PHP's built-in pi() function to reference pi. The pow() function can be used to calculate the square of the radius.

Finally, we store the calculated area of the circle in the $area variable. Finally, we use the echo statement to output the radius and area together.

If you want to extend this program, you can add an input field to let the user enter the radius size instead of the fixed 5. For example:

<!DOCTYPE html>
<html>
 <head>
  <title>计算圆的面积</title>
 </head>
 <body>
  <form method="post" action="<?php echo $_SERVER["PHP_SELF"];?>">
   半径：<input type="text" name="radius"><br>
   <input type="submit">
  </form>
  <?php
   if ($_SERVER["REQUEST_METHOD"] == "POST") {
    //通过$_POST获取输入的半径值
    $radius = $_POST[&#39;radius&#39;];
    $area = pi() * pow($radius, 2);
    echo "圆的半径是".$radius."，面积是".$area;
   }
  ?>
 </body>
</html>

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By adding the form and PHP form processing code, We can let the user input the radius size and our program will calculate the area of the circle based on this input. If the user enters 6, the program will output:

The radius of the circle is 6 and the area is 113.09733552923

Summary:

By using PHP to write programs, we can easily Calculate the area of a circle easily. To do this, we just need to use functions to reference pi, and variables to store and calculate the radius and area. This example shows that it is very convenient to use PHP to implement mathematical formulas.

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