When you call
move_uploaded_file($file_tmp,"uploads/".$file_name);
This creates a file in the uploads/ directory with the name of the file as it was named on the uploader’s computer.
Then you used sample code to add the attachment to phpMailer so you’re basically attempting to attach non-existent files.
These two lines:
$mail->addAttachment('uploads/file.tar.gz'); // I took this from the phpmailer example on github but I'm not sure if I have it right.
$mail->addAttachment('uploads/image.jpg', 'new.jpg');
should be changed to:
$mail->addAttachment("uploads/".$file_name);
Also note, it isn’t necessary to call move_uploaded_file if you don’t want to save the attachment after its uploaded and emailed. If that’s the case just call AddAttachment with $_FILES['image']['tmp_name'] as the file argument.
Also, in your HTML form, you have
<input id="file" name="file" type="file" />
but refer to the input as image in the code. You should change the name of that input from file to image.
To only attach the image and not save it take out the move_uploaded_file code and add:
$file_tmp = $_FILES['image']['tmp_name'];
$file_name = $_FILES['image']['name'];
//...
$mail->AddAttachment($file_tmp, $file_name);