public static function powmod($x, $y, $m) { switch (BigInt::support()) { case 'gmp': return gmp_powm($x, $y, $m); case 'big_int': return bi_powmod($x, $y, $m); case 'bcmath': return bcpowmod($x, $y, $m); case '': default: return BigInt::_powmod($x, $y, $m); } }