laravel notification php artisan webpush:vapid error

i install composer require laravel-notification-channels/webpush

when i try to generate php artisan webpush:vapid command then error like

Symfony\Component\Debug\Exception\FatalThrowableError  : Call to undefined function gmp_init()

at /opt/lampp/htdocs/pg_final/pgmanagment/vendor/web-token/jwt-util-ecc/NistCurve.php:50
    46|      * Returns an NIST P-256 curve.
    47|      */
    48|     public static function curve256(): Curve
    49|     {
> 50|         $p = \gmp_init('ffffffff00000001000000000000000000000000ffffffffffffffffffffffff', 16);
    51|         $a = \gmp_init('ffffffff00000001000000000000000000000000fffffffffffffffffffffffc', 16);
    52|         $b = \gmp_init('5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604b',  16);
    53|         $x = \gmp_init('6b17d1f2e12c4247f8bce6e563a440f277037d812deb33a0f4a13945d898c296', 16);
    54|         $y = \gmp_init('4fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5', 16);

Exception trace:

1   Jose\Component\Core\Util\Ecc\NistCurve::curve256()
        /opt/lampp/htdocs/pg_final/pgmanagment/vendor/minishlink/web-push/src/VAPID.php:178

2   Minishlink\WebPush\VAPID::createVapidKeys()
        /opt/lampp/htdocs/pg_final/pgmanagment/vendor/laravel-notification- channels/webpush/src/VapidKeysGenerateCommand.php:33

help me guys thanks