Methods in PHP to prevent direct access or viewing or downloading of the config.php file

Or, the design of PHP itself avoids directly viewing the file content? From a security perspective, what protection measures should be taken for this system-level file?
Perfect answer from a netizen
After research, we found the following commonly used methods:

1 Define an identification variable in the program

Copy the code The code is as follows:
define('IN_SYS', TRUE);


2 In config.php Get this variable in
Copy code The code is as follows:
if(!defined('IN_SYS')) {
exit('Access Forbidden');
}