<?php

class Circle
{    
    const PI = 3.14159265359;
 
    public function circumference($diameter)
    {
        return $diameter * self::PI;
    }
}

echo Circle::PI . PHP_EOL;

$circle = new Circle;
echo $circle::PI . PHP_EOL;
echo $circle->circumference(3) . PHP_EOL;

const PIE = 'Pizza Pie';
echo PIE;