It's easy to create a backdoor in an instant, the backdoor can be used in a remote process via a Linux terminal on the server that runs the PHP Language program.
Made to bypass the system that is disabled on the server, especially for reading sensitive files that are /etc/passwd
List of Remot3d Functions
Create backdoor for windows or linux servers (can run php file)
Bypass disable function's with imap_open vulnerability
Bypass read file /etc/passwd with cURL or Unique Logic Script's