steamid

    /*
    -- Function:    get_steamid64
    -- Purpose: Check whether we have a regular steam ID, or a 64 bit steam ID and return a 64 bit steam ID either way
    -- Arguments:   $steam_arg - Either a regular, or a 64 bit steam ID
    -- Returns: The 64 bit steam ID, or false if an invalid argument is provided
    */
    private function get_steamid64($steam_arg)
    {
        if (preg_match('/^STEAM_[0-9]:[0-9]:[0-9]{1,}/i', $steam_arg))
        {
            return $this->calculate_steamid64($steam_arg);
        }
        else if (preg_match('/^76561197960[0-9]{6}$/i', $steam_arg))
        {
            return $steam_arg;
        }
        else
        {
            return false;
        }
    }

    /*
    -- Function:    calculate_steamid64
    -- Purpose: Translate a steam ID to a 64 bit steam id as used by Valve
    -- Arguments:   $steam_id - The steam ID to translate
    -- Returns: The 64 bit steam ID, or false if an invalid steam ID is provided
    */
    public function calculate_steamid64($steam_id)
    {
        if (preg_match('/^STEAM_[0-9]:[0-9]:[0-9]{1,}/i', $steam_id))
        {
            $steam_id = str_replace("_", ":", $steam_id);
            list($part_one, $part_two, $part_three, $part_four) = explode(':', $steam_id);
            $result = bcadd('76561197960265728', $part_four * 2);
            $result = bcadd($result, $part_two);
            return bcadd($result, $part_three);
        }
        else
        {
            return false;
        }
    }

    /*
    -- Function:    calculate_steamid
    -- Purpose: Translate a 64 bit steam ID to a steam id as used by Valve
    -- Arguments:   $steam_id64 - The 64 bit steam ID to translate
    -- Returns: The steam ID, or false if an invalid 64 bit steam ID is provided
    */
    public function calculate_steamid($steam_id64)
    {
        if (preg_match('/^76561197960[0-9]{6}$/i', $steam_id64))
        {
            $part_one = substr( $steam_id64, -1) % 2 == 0 ? 0 : 1;
            $part_two = bcsub( $steam_id64, '76561197960265728' );
            $part_two = bcsub( $part_two, $part_one );
            $part_two = bcdiv( $part_two, 2 );
            return "STEAM_0:" . $part_one . ':' . $part_two;
        }
        else
        {
            return false;
        }
    }