&reftitle.constants; &extension.constants.core; MT_RAND_MT19937 (integer) Indicates that the correct Mt19937 (Mersenne Twister) implementation will be used by the algorithm, when creating a Random\Engine\Mt19937 instance using Random\Engine\Mt19937::__construct or seeding the global Mersenne Twister with mt_srand. MT_RAND_PHP (integer) Indicates that an incorrect Mersenne Twister implementation will be used by the algorithm, when creating a Random\Engine\Mt19937 instance using Random\Engine\Mt19937::__construct or seeding the global Mersenne Twister with mt_srand. The incorrect implementation is available for backwards compatibility with mt_srand prior to PHP 7.1.0.