universal select2 callback function for yii2

FunctionsController.php

<?php

namespace @app\your\namespace\controllers;

use Yii;
use yii\web\Controller;
use yii\filters\VerbFilter;
use yii\web\Response;
use yii\helpers\Json;

class FunctionsController extends Controller
{
    public function behaviors()
    {
        return [
            'verbs' => [
                'class' => VerbFilter::className(),
                'actions' => [
                    'select' => ['post'],
                ],
            ],
        ];
    }
    public static function actionSelect()
    {
        $request = Yii::$app->request;
        Yii::$app->response->format = Response::FORMAT_JSON;
        $req = Json::decode(Json::encode($request->post()),false);
        $id=$req->columns->id;
        $text=$req->columns->text;
        $model='@app\path\to\models\\'.$req->model;

        $query = $model::find();
        $all = filter_var($req->all,FILTER_VALIDATE_BOOLEAN);
        if ($all){$query->where(['<>',$text,'']);} // needed to bypass the override of the find function

        $query->select([$id,$text]);
        if ($req->q){$query->andFilterWhere(['like',$text,$req->q]);}

        if (count((array)$req->filters)){
            foreach ((array)$req->filters as $key=>$val){
                $query->andFilterWhere([$key=>$val]);
            }
        }
        $query->orderBy([$text => SORT_ASC]);
        $resp=[];
        foreach($query->all() as $entry){
            $resp[] = ['id'=>$entry->$id,'text'=>$entry->$text];
        }
        return $resp;
    }
}

view.php

<?= $form->field($model, 'teacher_tmp')->widget(Select2::classname(), [
        'options' => ['placeholder' => 'Some text...'],
        'pluginOptions' => [
            'ajax' => [
                'url' => '/your/url/functions/select',
                'dataType' => 'json',
                'method'=>'post',
                'data' => new JsExpression(' function(params) { return {
                          q:params.term,
                          model:"Modelname",
                          columns:{id:"id",text:"titleColumn"},
                          all:$("#all").prop("checked"),
                          filters:{
                              123:$("#123").val(),
                              456:$("#456").val(),
                          }
                         };}'),
                'processResults' => new JsExpression('function (data) {return {results: data};}'),
            ],
        ],
        'addon' => [
            'prepend' => [
                'content' => Html::checkbox('all', false, ['id'=>'all','title' => 'show all'])
            ],
        ]
    ]) ?>