- Some (but not all) settings in php.ini can be made in .htaccess, but they must be made with php_value and php_flag directives (php_flag for boolean settings, php_value for others) because .htaccess is an Apache file, not PHP. See http://docs.moodle.org/en/Installing_Moodle#Using_a_.htaccess_file_for_webserver_and_PHP_settings
- Only php.ini settings that are classified as PHP_INI_PERDIR or PHP_INI_ALL can be made this way. But PHP extensions are not settings at all, and cannot be made in .htaccess.
- You said, "They say that I can access php.ini." Did you mean that you cannot access php.ini? Well, that's what I said, but the question was whether they supported the creation of custom php.ini files. At this point, I will assume that you did ask that and the answer was no.
- So unless you can get your host to install the PHP extensions that Moodle requires, you will need to find another host.