PHPMailer doesn't work when use json_encode

I have really big problem with this json_encode which need use inside foreach loop which is inside if statement. However, if I need to send mail just to one person, json_encode is very easy, but the problem is because I need to get email addresses from database and so I first check if mail count is greater than zero and later use foreach loop for send mail to specified db query. So, for properly encode this php array of $data I think that this need stay outside of if mail count is greater than zero. Otherwise, I get error in console AJAX error:parseerror and Syntax error: Unexpected end of JSON input. Perhaps, if this statement of php array $data it's outside of statement mail count is greater than zero then json_encode work very well. When a form is submitted I get correct response on the web page, in console and in network tab, but email isn't sent. However, if I comment js file, when a form is submitted, email is sent correctly on every page, all data it's inserted into db and perhaps this content of $data it's displayed successfully, but I need AJAX for this, so please can you check this my php file and try to help me, because I can not figure out more where is the error and how to fix it. I was read complete google, but dont exist even 1 exemple of how to use json when send mail to multiple recipients, or when get recipients from db etc. I can not figure out more how to fix this problem. Perhaps, I think too that this statement if($error==false) need stay inside if(mailOwner->sent), but in this case how to write else?! So complicated for me, that can not understand anything more. So, this is complete code of php file.

<?php
/*ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);*/
// define variables and set to empty values
$fname = $tel = $userMail = $userMessage = $email_address_id ="";
$fname_error = $tel_error = $userMail_error = $userMessage_error = "";
$error = false;
//Load the config file
$dbHost = "localhost";
$dbUser = "secret";
$dbPassword = "secret";
$dbName = "visitneum";
$dbCharset = "utf8";
try{
    $dsn = "mysql:host=" . $dbHost . ";dbName=" . $dbName . ";charset=" . $dbCharset;
    $pdo = new PDO($dsn, $dbUser, $dbPassword);
    array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8");
    $pdo->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
    //echo "connected!";
}catch(PDOException $e){
    echo "Greška u konekciji: " . $e->getMessage();
}     
use PHPMailer\PHPMailer\PHPMailer;
require 'PHPMailer/PHPMailer.php';
require 'PHPMailer/SMTP.php';
require 'PHPMailer/Exception.php';

if($_SERVER['REQUEST_METHOD'] == 'POST'){
    if (isset($_POST['submitOwner'])) {
    $fname = $_POST['fname'];
    $tel = $_POST['tel'];
    $userMail = $_POST["userMail"];
    $userMessage = $_POST["userMessage"];

    if(empty($_POST["fname"])) {
        $error=true;
        $fname_error = "Ime i prezime ne može biti prazno!";
    }else{
        $fname = $_POST['fname'];   
        if(!preg_match("/^[a-zšđčćžA-ZŠĐČĆŽ\s]*$/", $fname)){
            $fname_error = "Ime i prezime mogu da sadrže samo slova i razmak!";
        }
    }
    if(empty($_POST["tel"])) {
        $tel_error = "Broj telefona ne može biti prazan!";
    }else{
        $tel = $_POST['tel'];
        if(!preg_match('/^[\+]?[0-9]{9,15}$/', $tel)) {
            $tel_error = "Broj telefona treba da sadrži minimalno od 9 do 15 brojeva!";
        }
    }
if(empty($_POST["userMail"])){
        $userMail_error = "E-mail ne može biti prazan!";
    }else{
        $userMail = $_POST["userMail"];
        // check if e-mail address is well-formed
        if(!filter_var($userMail, FILTER_VALIDATE_EMAIL)) {
            $userMail_error = "E-mail adresa nije ispravna!";
        }
    }
    if(empty($_POST["userMessage"])) {
        $userMessage_error = "Sadržaj poruke ne može biti prazan!";
    }else{
        $userMessage = $_POST["userMessage"];
        if(!preg_match("/^[a-zšđčćžA-ZŠĐČĆŽ0-9 ,.!?\'\"]*$/", $userMessage)){
            $userMessage_error = "Sadržaj poruke ne mogu biti specijalni znaci!";
        }
    }
    if($fname_error == '' && $tel_error == '' && $userMail_error == '' && $userMessage_error == ''){
    // Instantiate a NEW email
    $mailOwner = new PHPMailer(true);
    $mailOwner->CharSet = "UTF-8";
    //SMTP Settings
    $mailOwner->isSMTP();
    $mailOwner->Host = 'mail.visit-neum.com';
    $mailOwner->SMTPAuth = true;
    //$mailOwner->SMTPDebug = 2;
    $mailOwner->Username = 'secret';
    $mailOwner->Password = 'secret';
    $mailOwner->Port = 465; // 587
    $mailOwner->SMTPSecure = 'ssl'; // tls
    $mailOwner->WordWrap = 50;  
    $mailOwner->isHTML(true);
    $mailOwner->setFrom('secret');
    $mailOwner->clearAddresses();
    $mailOwner->smtpClose();
    $mailOwner->Subject = "Nova poruka od visit-neum.com";
// SELECT email values from database for man owners of others property(restaurants, ships, etc)
    $query_m = "SELECT owners_email.email_address_id, email_address, owner_name, owner_property, owner_sex,
    owner_type FROM visitneum.owners_email INNER JOIN visitneum.pages ON (pages.email_address_id = owners_email.email_address_id) WHERE `owner_sex`='M' AND `owner_type`='other' AND `pages_id` = ?";
    $dbstmt = $pdo->prepare($query_m);
    $dbstmt->bindParam(1,$pages_id);
    $dbstmt->execute();
    //var_dump($dbstmt);
    //get emails from db via pdo
    $emails_other = $dbstmt->fetchAll(PDO::FETCH_ASSOC);
    if(is_array($emails_other) && count($emails_other) > 0) {
    foreach ($emails_other as $email_other){
        //var_dump($email_other['email_address']);
            $mailOwner->addAddress($email_other['email_address']);
                $body_other = "<p>Poštovani {$email_other['owner_name']}, <br>" . "Upravo ste primili poruku sa sajta <a href='https://www.visit-neum.com'>visit-neum.com</a><br>Detalji Vaše poruke se nalaze ispod:</p><p><strong>Od: </strong>" . ucwords($fname) . "<br><strong>Telefon: </strong>" . $tel . "<br><strong>E-mail: </strong>" .strtolower($userMail)."<br><strong>Poruka: </strong>" . $userMessage . "<br><br><strong>Napomena: </strong>Molimo Vas da na ovu poruku ne odgovarate. Vaš odgovor pošaljite na: " . strtoupper($userMail) . "</p>";
                $mailOwner->Body = $body_other;
                if($mailOwner->send()){
                    $mailOwner = "INSERT INTO visitneum.contact_owner (fname, tel, userMail, userMessage, email_address_id) VALUES (:fname, :tel, :userMail, :userMessage, :email_address_id)";
                    $stmt = $pdo->prepare($mailOwner);
                    $stmt->execute(['fname' => $fname, 'tel' => $tel, 'userMail' => $userMail, 'userMessage' => $userMessage, 'email_address_id' => $email_other['email_address_id']]); 
                    }//end if mail send
    }//end foreach for email addresses  (man owners of other properties(restaurants, ships etc.))
}//end if for array of emails

    if($error==false){
        $data['response'] = "success";
        $data['content'] = "Hvala Vam " . ucwords($fname) . "! Vaša poruka je uspješno poslata vlasniku objekta! Odgovor ćete dobiti ubrzo!";
        $jsonData = $data;
    }//end if $error==false*/
else{
    $data['response'] = "error";
    $data['content'] = "Došlo je do greške! Pokušajte ponovo..." . $mailOwner->ErrorInfo;
    $jsonData = $data;
}
//header("Content-Type: application/json; charset=utf-8", true);
echo json_encode($jsonData);
exit();

    }//end if validation
}//end submitOwner
}//end REQUEST METHOD = POST

Any kind of help will be highly appreciated and thanks in advance.