ELO Rating using PHP as base Backend Language..

elorating.php

<?php
class elo{
	//K Factor = 32 (below 2100)
	//K Factor = 24 (between 2100 and 2400)
	//K Factor = 16 (above 2400)
	const KFACTOR = 32;
	//WIN = 1 Points
	//DRAW = 0.5 Points
	//LOSE = 0 Points
	const WIN = 1;
	const DRAW = 0.5;
	const LOSE = 0;
	//
	protected static $_expectedScore = [];
	protected static $_newRating = [];
	protected $_rating = [];
	public static function powMod($_base,$_exponent){
		$_result = 1;
		for($_g = 0;$_g < $_exponent;$_g++){
			$_result *= $_base;
		}
		return($_result);
	}
	public function rating($_rA,$_rB){
		$this->_rating["rate"] = self::getExpectedScores($_rA,$_rB);
		return($this->_rating);
	}
	public static function getNewRatings($_rA,$_rB,$_sA,$_sB,$_eA,$_eB){
		self::$_newRating["a"] = $_rA + (self::KFACTOR * ($_sA - $_eA));
		self::$_newRating["b"] = $_rB + (self::KFACTOR * ($_sB - $_eB));
		return(self::$_newRating);
	}
	public static function getExpectedScores($_rA,$_rB){
		$_sA = self::WIN;
		$_sB = self::LOSE;
		self::$_expectedScore["a"] = 1 / (1 + (self::powMod(10,($_rA - $_rB) / 400)));
		self::$_expectedScore["b"] = 1 / (1 + (self::powMod(10,($_rB - $_rA) / 400)));
		$_eA = self::$_expectedScore["a"];
		$_eB = self::$_expectedScore["b"];
		self::$_expectedScore["c"] = self::getNewRatings($_rA,$_rB,$_sA,$_sB,$_eA,$_eB);
		return(self::$_expectedScore);
	}
}
$_rA = 1200;
$_rB = 1200;
$_c = new elo();
print_r($_c -> rating($_rA,$_rB));
//print_r(elo::getExpectedScores($_rA,$_rB));
?>