if($_POST){
try{

........

send();

}} catch (Exception $e) {
    echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
    die();
}
}

try {
    //Server settings
    $mail->SMTPDebug = 0;                      //Enable verbose debug output
    $mail->isSMTP();                                            //Send using SMTP
    $mail->Host       = 'smtp.gmail.com';                     //Set the SMTP server to send through
    $mail->SMTPAuth   = true;                                   //Enable SMTP authentication
    $mail->Username   = 'xxxxx';                     //SMTP username
    $mail->Password   = 'xxxxx';                               //SMTP password
    $mail->SMTPSecure = PHPMailer::ENCRYPTION_SMTPS;            //Enable implicit TLS encryption
    $mail->Port       = 465;                                    //TCP port to connect to; use 587 if you have set `SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS`
    //Recipients
    $mail->setFrom('xxxxx', 'Destek Talebi');
    $mail->addAddress('xxxxx', 'xxxx');     //Add a recipient
    //Content
    $mail->isHTML(true);
    $mail->CharSet = "UTF-8";
    $mail->Subject = $mail_form_konu;
    $mail->Body    = $mail_icerik;
    $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';
    $mail->send();
    echo 'Message has been sent';
    
} catch (Exception $e) {
    echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
    die();
}