What is the difference between php.ini and .htaccess?

Question

Assume if I want to change the value of

php_value post_max_size 20M in .htaccess

post_max_size 20M in php.ini

Both will do same operation. So

Answer 1

Not an answer to your question, but an interesting tidbit I didn't know myself, when using PHP on Windows, it is possible to set per-directory settings in the registry. From the manual:

Changing PHP configuration via the Windows registry

When running PHP on Windows, the configuration values can be modified on a per-directory basis using the Windows registry. The configuration values are stored in the registry key HKLM\SOFTWARE\PHP\Per Directory Values, in the sub-keys corresponding to the path names. For example, configuration values for the directory c:\inetpub\wwwroot would be stored in the key HKLM\SOFTWARE\PHP\Per Directory Values\c\inetpub\wwwroot. The settings for the directory would be active for any script running from this directory or any subdirectory of it. The values under the key should have the name of the PHP configuration directive and the string value. PHP constants in the values are not parsed. However, only configuration values changeable in PHP_INI_USER can be set this way, PHP_INI_PERDIR values can not.