If I use a shared hosting, can I really set all value on my php.ini file in the runtime?

Question

Something like:

ini_set("display_errors", 1);

Answer 1

You can set some of them, others can not be set for security reasons, such as allow_url_fopen.

Answer 2

Here is the list of all the php.ini directives, and where they can be changed from:

http://php.net/manual/en/ini.list.php