apache - htaccess change DirectoryIndex priority to php and not html -

1. in production server there index.html , index.php
2. by default index.html getting loaded.
3. i want index.php default script load , if index.php not present index.html can load.
4. it shared hosting not have access httpd.conf file

5. so thought of creating .htaccess file above condition.

   what directive include in .htaccess file so?

besides, here explaining reason above.

1. the php project done in codeigniter framework.
2. in sub folder root have oscommerce.
3. we not have index.html there , index.php present.
4. periodically index.html created means has iframe code.
5. the client reports , keep deleting index.html file
6. we have changed ftp password.
7. so thought temp solution make index.php loaded default instead of index.html

as per apache documentation directoryindex, put following in .htaccess file in same directory index.php:

directoryindex index.php index.html