$password           =     ($_POST["password"]);

$iterations = 1000;

$salt = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);

$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);

$password           =     ($_POST["password"]);

$iterations = 1000;

$salt = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);

$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
$myrow['password'] === $hash// тут не правильно сравнивает

password_hash($password, PASSWORD_DEFAULT);