App\Providers\ValidatorExtendServiceProvider::boot PHP Method

    public function boot()
    {
        /**
         * @param $a     attribute
         * @param $value value
         * @param $p     parameters
         * @param $v     validator
         */
        Validator::extend('username', function ($a, $value, $p, $v) {
            return preg_match("/^([A-Za-z0-9\\x{4e00}-\\x{9fa5}_]+)\$/u", $value);
        });
        Validator::extend('nickname', function ($a, $value, $p, $v) {
            return $value == addslashes(trim($value));
        });
        Validator::extend('no_special_chars', function ($a, $value, $p, $v) {
            return $value == addslashes(trim($value));
        });
        Validator::extend('playername', function ($a, $value, $p, $v) {
            return preg_match("/^([A-Za-z0-9_]+)\$/", $value);
        });
        Validator::extend('pname_chinese', function ($a, $value, $p, $v) {
            return preg_match("/^([A-Za-z0-9\\x{4e00}-\\x{9fa5}_]+)\$/u", $value);
        });
        Validator::extend('preference', function ($a, $value, $p, $v) {
            return preg_match("/^(default|slim)\$/", $value);
        });
        Validator::extend('model', function ($a, $value, $p, $v) {
            return preg_match("/^(steve|alex|cape)\$/", $value);
        });
    }