How to add and remove extensions from extension groups in phpBB3
In this article we'll show you how to add more file formats to the existing extension groups in phpBB3, and how to remove them. Extension groups are used to combine similar file formats: e.g. images, archives, documents, etc. With the different extension groups and the extension types that are in them you have control over what file formats are allowed as attachments and where they can be attached (e.g. posts, private messages).
By default, there are several preconfigured extension groups in phpBB3. Each consists of a number of extensions. Most of these groups, with the exception of Images and Archives, are not allowed as attachments by default. However, you can allow any of the extension groups. For more information on this check out the article on allowing attachments in private messages and allowing extension groups.
As we mentioned, each group consists of different file formats. You can expand the list by adding more extensions, or you can remove extensions. To do this, log in to the administration control panel, click on the Posting tab and then on the Manage extensions link on the left. You'll see a table with the extension groups and the extensions in each group. To delete an extension, mark the Delete checkbox next to the name of the extension and click on the Submit button at the bottom of the page.
At the top of the page there's a panel labeled Add extension. To add an extension, type the extension in the text field for Extension, and from the Extension group drop-down menu select the appropriate group. For example, we want to add the BMP image format to the Images extension group, so we type bmp in the Extension text field and from the drop-down menu we select Images. Then we click on the Submit button in the lower right corner of the Add extension panel, and that's it. The new extension will be listed in the table below.
It's not recommended to add scripts (e.g. PHP) as allowed extensions.