About php's allow_url_fopen and safe_mode functions

When installing dedecms, I noticed that the system requires two functions, so take a look at the definitions of these two functions:

allow_url_fopen

allows functions like fopen to open urls.

Here is a more official explanation:
http://php.net/manual/zh/filesystem.configuration.php

safe_mode

PHP’s safe mode is a very important built-in security mechanism that can control some functions in PHP, such as system(),
At the same time, the permissions of many file operation functions are controlled, and certain key files, such as /etc/passwd, are not allowed.
​But the default php.ini does not open safe mode, let’s open it:
​safe_mode = on

For more details, please refer here:
http://www.jb51.net/article/31040.htm
http://blog.csdn.net/tangxi383367315/article/details/7722086
http://www.phpddt.com/php/643.html

The above introduces the allow_url_fopen and safe_mode functions of PHP, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.