.htaccess file doesn't exist - php

Question

I am beginner in web development. I launched website from hostgator. in my index.php I used phpmailer but when I click send button "HTTP ERROR 500" appears. I think it happens because I don't have .htaccess file. I am searching now but can't find .htaccess example to add to my project. can somebody show me an example of .htaccess? and also tell me where to add it - homepage or my website project directory where index.php exists?
in my index.php file I started from bootstrap template and modified by myself. purpose of .htaccess file is to send emails with phpmailer. here is my index.php document:
<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exceptions;
require 'phpmailer/src/Exceptions.php';
require 'phpmailer/src/PHPMailer.php';
require 'phpmailer/src/SMTP.php';
if(isset($_POST["send"])){
$mail = new PHPMailer(true);
$mail->isSMTP();
$mail->Host = 'smtp.gmail.com';
$mail->SMTPAuth = true;
$mail->Username = 'info#mil-data.com';
$mail->Password = 'dgqncmczasdygmwjwbr';
$mail->SMTPSecure = 'ssl';
$mail->Port = 465;
$mail->setForm('info#mil-data.com')
$mail->addAddress($_POST["email"]);
$mail->isHTML(true);
$mail->Subject = $_POST["subject"];
$mail->Body = $_POST["message"];
$mail->send();
echo
"
<script>
alert('Sent Successfully');
document.location.href = 'index.php'
</script>
";
}

Answer 1

You can read this article, there it shows an htaccess and also explains a bit of its operation, and you can also check this htaccess generator: https://julianpoemp.github.io/ngx-htaccess-generator/#/generator