WordPress stops executing code after the require() method

I noticed that require(), require_once(), include() and include_once() methods were somehow not working. The files that were called using these methods were not being called and the code stopped executing forward from this point.

After a lot of Googling and R&D I didn’t find any solution to making the above methods work.

So I decided to look into the architecture of the tweentysixteen theme and found out that there was a built in function of WordPress that it used to include other PHP files.

So I thought of trying that out to include the class.PHPMailer.php and PHPMailerAutoload.php files. If changed the lines

require("PHPMailer/class.PHPMailer.php");
require 'PHPMailer/PHPMailerAutoload.php';

in my code to,

get_template_part('PHPMailer/class.PHPMailer');
get_template_part('PPHPMailer/PHPMailerAutoload');

and finally I was able to fix the issue and the contact form started working.