Here is the code snippet [ for PHP, Slim Framework on server side ]

In routes.php

To fetch data

    $app->get('/tablename/connection', function (Request $request, Response $response)
    {
        $db = $this->get(PDO::class);
        $sql = "SELECT sendstatus FROM tablename";
        $exec_sql = $db->prepare($sql);
        $exec_sql->execute();

        $data = $exec_sql->fetchAll(PDO::FETCH_ASSOC);
        $data_encode = json_encode($data);
        $response->getBody()->write($data_encode);
        return $response->withHeader('Content-Type', 'application/json');
    }); 

To post data

    $app->post('/tablename/insertVehicleEnquiry', function (request $request, response $response)
    {
        $db = $this->get(PDO::class);
        $data = json_decode($data, true);
        $fieldpk = isset( data[0] ["fieldpk"] ) ? $data[0]["fieldpk"] : null ;
        $field1  = isset( $data[0]["field1"]  ) ? $data[0]["field1"]  : null ; 
        $query = "INSERT INTO tablename_header ( " ;
        $query = $query . "fieldpk)" ;
        $query = $query . "VALUES (" ;
        $query = $query . "'".$vehicleenquiryheaderpk_header."') ";

        $exec_sql = $db->prepare($query); 
         
        try
        {
           $exec_sql->execute();
           $recordcount_header_check = $recordcount_header_check + 1 ;
        }
        catch(PDOException $return_errorMessage)
        {
            $db->rollBack();
            $return_arr[] = array('return_status' => 400,
                                  'success_message' => '',
                                  'error_message' => $return_errorMessage->getMessage()
                                 ); 
           
            $data_encode = json_encode($return_arr);
            $data_encode = encrypt_decrypt('encrypt', $data_encode);
            $response->getBody()->write($data_encode);
            return $response->withHeader('Content-Type', 'application/json');
        }
        $db->commit();
        $return_arr[] = array('return_status' => 200,
                              'success_message' => 'Successful',
                              'error_message' => ''
                              ); 
        $data_encode = json_encode($return_arr);
        $data_encode = encrypt_decrypt('encrypt', $data_encode);
        $response->getBody()->write($data_encode);
        return $response->withHeader('Content-Type', 'application/json');
    ); 

I've simplified the server side code to a maximum extend.  For this, you need to go through Slim framework, IMO. 

HTH