First TwoPlayerTrueSkillCalculator unit test passed

PHPSkills/Elo/FideEloCalculator.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Moserware\Skills\Elo;
+
+require_once(dirname(__FILE__) . "/TwoPlayerEloCalculator.php");
+require_once(dirname(__FILE__) . "/FideKFactor.php");
+
+/** Including ELO's scheme as a simple comparison. 
+ *  See http://en.wikipedia.org/wiki/Elo_rating_system#Theory
+ *  for more details
+ */
+class FideEloCalculator extends TwoPlayerEloCalculator
+{
+    public function __construct(FideKFactor $kFactor)        
+    {
+        parent::__construct($kFactor);
+    }
+
+    public static function createWithDefaultKFactor()
+    {
+        return new FideEloCalculator(new FideKFactor());
+    }
+
+    public static function createWithProvisionalKFactor()
+    {
+        return new FideEloCalculator(new ProvisionalFideKFactor());
+    }
+
+    public function getPlayerWinProbability($gameInfo, $playerRating, $opponentRating)
+    {
+        $ratingDifference = $opponentRating - $playerRating;
+
+        return 1.0
+               /
+               (
+                   1.0 + pow(10.0, $ratingDifference / (2 * $gameInfo->getBeta()))
+               );
+    }        
+}
+
+?>