Example: How to Find Area of a Circle with Diameter in PHP using the pi() & pow() function

C
C++
C#
Java
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PHP

<?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";
?>