Smopp_v2/tmc/ajax/get_cell.php

<?php /** Created by Anton on 15.02.2020. */

use yii\db\Query;
use app\models\entity\Tmc;
use app\models\entity\Storage;

require '../yiiInit.php';

$inventoryNum = (int)Yii::$app->request->post('num');
$query = new Query();
$query->select('ts.title')
    ->from(Tmc::tableName() . ' tt')
    ->leftJoin(Storage::tableName() . ' ts', 'tt.storage = ts.id')
    ->where(['inventory_num' => $inventoryNum])
;
$result = $query->one();

if ($result) {
    echo $result['title'];
} else {
    echo '404';
}