PHPMailer autoload.php not able to open - php

Question

I am currently hosting a website on GoDaddy and recently I added a contact form that will send me emails when people fill it out. It works perfectly when I use XAMPP, but once I uploaded the same code onto the GoDaddy servers, it gives me a HTTP ERROR 500.
I am using PHPMailer and Gmail's SMTP service. This is the current code that works with XAMPP:
<?php
require_once "vendor/autoload.php";
$name = $_POST["name"];
$email_from = $_POST["email"];
$telephone = $_POST["telephone"];
$message = "Name: ".$name."\r\n".
"Email: ".$email_from."\r\n".
"Telephone: ".$telephone."\r\n";
$email_to = "myemail#gmail.com";
if(isset($_POST['submit'])){
$mail = new PHPMailer\PHPMailer\PHPMailer;
$mail->isSMTP();
$mail->Host = "smtp.gmail.com";
$mail->SMTPAuth = true;
$mail->Username = "myemail#gmail.com";
$mail->Password = "password";
$mail->SMTPSecure = "tls";
$mail->Port = 587;
$mail->From = $email_from;
$mail->FromName = $name;
$mail->addAddress($email_to);
$mail->addReplyTo($email_from);
$mail->Subject = "Info";
$mail->Body = $message;
if ($_POST["submit"]){
if(!$mail->send()){
echo "Mailer error: " . $mail->ErrorInfo;
}
else{
echo "Message sent successfully";
}
}
}
Since it was giving me HTTP ERROR 500, I decided to look into the error logs given by GoDaddy. This is the error:
[13-Dec-2018 19:33:13 UTC] PHP Fatal error: require_once(): Failed opening required '/home/namesearch/public_html/vendor/composer/autoload_real.php' (include_path='.:/opt/alt/php56/usr/share/pear:/opt/alt/php56/usr/share/php') in /home/namesearch/public_html/vendor/autoload.php on line 5
Please help!!! I have looked up countless solutions and I just don't know how to fix it. I even tried putting my path as: /home/namesearch/public_html/vendor/composer/autoload_real.php and /home/namesearch/public_html/vendor/composer/autoload.php but nothing works.

Answer 1

I'm adding on the comment from #h2oooooo here. This is something that drove me insane when I first started learning composer. As he said above, make sure you've uploaded all of your dependencies, and then updates your autoload files. But, here's exactly how to do that:
1) Go to the root of your project in your local environment.
2) Then run composer update
3) I recommend just uploading the entire project again, unless you use filezilla folder compare to show which files are different, it'll be hard to know for sure.
If you're uploading your project from a git repo, then double check that your .gitignore file isn't ignoring your /vendor folder, as it often does by default.

Answer 2

I had a similar problem with configuring mustache so I hope this helps. My problem was with this line:
require_once "vendor/autoload.php";
It wasn't picking up the correct PHP include path.
Add the absolute path of the folder one level before vendor to your PHP include path.
Place this code right before the require.
$includePath = get_include_path() . ";ABSOLUTE PATH OF FOLDER ONE LEVEL BELOW VENDOR";
set_include_path($includePath);