Understand the usage of static and const keywords in php5

class Counter
{
 private static $count = 0; //Define a static property
 const VERSION = 2.0; //Define a constant
 //Constructor
 function __construct(){
 self::$count++;
 }
 //Destructor
 function __destruct(){
 self::$count--;
 }
 //Define a static method
 static function getCount(){
 return self ::$count;
 }
}
//Create an instance
$c = new Counter();
//Perform printing
print( Counter::getCount(). " " ); //Use Directly enter the class name to access the static method Counter::getCount
//Print the version of the class
print( "Version used: " .Counter::VERSION. " " );
?>