Miso

<?php

    $znacka = $_POST['znacka1'];
    $model = $_POST['model1'];
    $spz = $_POST['spz1'];

    $con = mysqli_connect('localhost:3306', 'root', '', 'KnihaJazd');
    $response = [];

        // Check for valid input
    if($znacka && $model && $spz){
        // Execute query to insert
        if(mysqli_query($con, "INSERT INTO vp (znacka, model, spz) VALUES ('{$znacka}', '{$model}', '{$spz}');")){
            $response['success']['msg'] = 'Data were successfully added';
            $response['success']['data'] = [
                'znacka' => $znacka,
                'model' => $model,
                'spz1' => $spz
            ];
        }else{
            $response['error']['sql'] = 'Sql error: '. mysqli_error($con);
        }
    }else{
        if(!$znacka) $response['error']['znacka'] = "znacka were not provided!";
        if(!$model) $response['error']['model'] =  "model were not provided!";
        if(!$spz) $response['error']['spz'] =  "spz were not provided!";
    }

    // Close connection
    mysqli_close($con);
    echo json_encode($response);

?>