Write a PHP Script to calculate the area of Circle, Square, and Rectangle.
<?php
// Circle
$radius = 5;
$area_circle = pi() * $radius * $radius;
// Square
$side = 4;
$area_square = $side * $side;
// Rectangle
$length = 6;
$width = 3;
$area_rectangle = $length * $width;
// Display Results
echo "Area of Circle: " . $area_circle . "<br>";
echo "Area of Square: " . $area_square . "<br>";
echo "Area of Rectangle: " . $area_rectangle;
?>