BookStack\Role::permissions PHP Method

    public function permissions()
    {
        return $this->belongsToMany(RolePermission::class, 'permission_role', 'role_id', 'permission_id');
    }

 /**
  * Assign an list of permission names to an role.
  * @param Role $role
  * @param array $permissionNameArray
  */
 public function assignRolePermissions(Role $role, $permissionNameArray = [])
 {
     $permissions = [];
     $permissionNameArray = array_values($permissionNameArray);
     if ($permissionNameArray && count($permissionNameArray) > 0) {
         $permissions = $this->permission->whereIn('name', $permissionNameArray)->pluck('id')->toArray();
     }
     $role->permissions()->sync($permissions);
 }