steam api, convert steamID64

<?php 
 
/** 
 * Class SteamID 
 * Simple PHP SteamID converter class that converts between SteamID's and Steam CommunityID's 
 * 
 * @author Callum Thomson <callum@callumthomson.co.uk> 
 * @version 3.0.0 
 */ 
class SteamIDConverter { 
    /** 
	 * Make a decision based on the input which conversion function should be run and then call it with the data. 
	 * 
     * @param $id SteamID or CommunityID 
	 * @return string Converted ID 
     */ 
    public static function convert($id) 
	{ 
		if(strpos($id, 'STEAM')===false)  
		{ // It's a CommunityID 
			return self::getIDFromCommunity($id); 
		} 
		else 
		{ // It's a SteamID 
			return self::getCommunityFromID($id); 
		} 
	} 
    /** 
	 * Convert SteamID into a CommunityID 
	 * 
     * @param $id SteamID 
     * @return string CommunityID 
     */ 
    private  static function getCommunityFromID($id) 
	{ 
		$accountarray	=	explode(":", $id); 
		$idnum			=	$accountarray[1]; 
		$accountnum		=	$accountarray[2]; 
		$constant		=	'76561197960265728'; 
		$number			=	bcadd(bcmul($accountnum, 2), bcadd($idnum, $constant)); // ($accountnum *2) + ($idnum + $constant) 
		return $number; 
	} 
    /** 
	 * Convert CommunityID to SteamID 
	 * 
     * @param $id CommunityID 
     * @return string SteamID 
     */ 
    private static function getIDFromCommunity($id) 
	{ 
		$idnum		=	'0'; 
		$accnum		=	'0'; 
		$constant	=	'76561197960265728'; 
		if(bcmod($id, '2')==0) 
		{ 
			$idnum	=	'0'; 
			$temp	=	bcsub($id, $constant); 
		} 
		else 
		{ 
			$idnum	=	'1'; 
			$temp	=	bcsub($id,bcadd($constant, '1')); 
		} 
		$accnum	=	bcdiv($temp, '2'); 
		return 		"STEAM_0:".$idnum.":".number_format($accnum, 0, '', ''); 
	} 
} 
 
echo SteamIDConverter::convert('76561198091655275');