PHP Code:

<?php
class ConstantExample
{
    const CONSTANT = "value unchanged";

    function constantInFunction() {
        echo  self::CONSTANT; // Constant variable is accessible inside function of Class
    }
}

echo ConstantExample::CONSTANT; // Constant variable is accessible outside of Class

$classname = "ConstantExample";
echo $classname::CONSTANT; // As of PHP 5.3.0, Constant variable is accessible by Class variable

$classObj = new ConstantExample();

echo $classObj::CONSTANT."\n"; // As of PHP 5.3.0, Constant variable is accessible by Class object
?>