I'm currently trying to get data from the DB with a Laravel controller through a model Maintain. Is there a way to query the DB based on the request data made by an axios post from the front end, this includes both variables sub and zone, I have the ability to get the data from using sub OR zone but not both, is there a way to construct a multi where query if $request contains the necessary variables and a standard request if they are null or ""?

  public function all(Request $request){
    $query = [];
    if($request->sub != ""){
      array_push($query, ['subsystem', '=', $request->sub]);
    }
    if($request->zone != ""){
      array_push($query, ['zone', '=', $request->zone]);
    }

    if(count($query) > 0){
      return Maintain::all()->where($query);
    }
    else{
      return Maintain::all();
    }
  }

Currently This returns with an error ErrorException: array_key_exists(): The first argument should be either a string or an integer in file but I've been using the Laravel reference and it doesn't seem to be working. I used Postman to get the readout of $query and it contains the following:

[
 ['sub', '=', 'Subsystem 1'],
 ['zone', '=', 'Zone 1']
]

Any help would be appreciated.