What php-based forum engine is recommended for hosting a closed company forum on external servers while meeting the following requirements:
- Limiting access to authorized users only
- Creating subforums with selective user visibility based on user groups, such as management and others.



forum engine that can handle user authentication and authorization efficiently. Additionally, the forum engine should have customizable permissions that allow for granular control over user access to different forum sections.

From what I recall, most forum engines offer optional authorized access to information. My suggestions for a forum engine are as follows:
- phpBB (free)
- vBulletin (paid)
- Invision Power Board (paid)

 While free options like phpBB can be great for budget-conscious organizations, paid options such as vBulletin and Invision Power Board may offer additional benefits, such as dedicated support and more advanced customization options. Ultimately, the choice will depend on your specific needs and preferences.

In reality, most engines can meet your needs. Previously, I found Burning Board to be a suitable option for this purpose, as it allowed HTML in threads and had extensive tag support. The lite version of the engine is available for free.
As for our organization, we have opted to use vBulletin.

While the choice of forum engine will largely depend on the specific needs of the organization or community, it's important to consider the features and functionalities of each engine before making a final decision. For example, if extensive customization options are needed, Burning Board may be a solid choice. However, if you prioritize stability and support, vBulletin may be more suitable. Ultimately, it's about finding the right balance between affordability, functionality, and ease of use.

If you are considering paying for vBulletin, I recommend taking a look at XenForo as well (xenforo.com/). However, most popular forum engines offer the necessary functionality.
One of the major advantages of XenForo is its superior architecture and code, which sets it apart from other commercial engines. In my experience, it surpasses free engines like SMF and phpBB by a significant margin.
That being said, if expansion of functionality is not in the plans, any engine may suffice.

While XenForo may be a solid investment for organizations seeking advanced customization options and scalability, other engines like vBulletin may be suitable for smaller communities with more limited functionality requirements. Ultimately, careful consideration of the features, functionality, and scalability of each engine is crucial to making an informed decision.

phpBB is one of the most well-known and widely-used forum engines. Its free availability and large community have enabled developers to create a wide range of improvements including modules and design options, thereby extending the engine's functionality. This user-friendly CMS is well-suited for medium-sized non-profit forums, with a range of useful functions already included in the basic configuration.

Constant updates and refinements keep the platform current - the latest version (3.2) was released in January 2017. The downside to the engine's popularity is that it attracts many spam bots, making it necessary to focus on spam prevention and system security.

Another platform to consider is PunBB, which is lightweight and well-suited to small projects. Although its functionality is limited, this is outweighed by the speed and ease-of-use, making it a great option for those looking for a compact solution.

Simple Machines Forum (SMF) is another free engine that offers fast page loading and a simple interface. Unlike other free engines, SMF has been secure against hacking attacks, though commercial engine alternatives do provide greater security.

The IPS Community Suite, while paid, is popular among Western and Russian-speaking communities for its range of plugins and integration options, including chat, image galleries, and blog integration.

Ultimately, the choice will depend on the specific needs of the organization or community. Free options like phpBB and SMF may be suitable for smaller forums, while paid options such as the IPS Community Suite may offer more extensive functionality for larger organizations. It's important to carefully consider the features and scalability of each engine before making a final decision.

I would recommend the use of the phpBB forum software for hosting a closed company forum on external servers, catering to the specific needs you have outlined.
phpBB stands out in its ability to efficiently handle user authentication and authorization. It provides robust features that allow the forum administrator to restrict access to authorized users only. With options to configure user registration to require approval, phpBB ensures that only approved members can gain access to the forum, making it an ideal solution for a closed company forum.

When it comes to creating subforums with selective user visibility based on user groups, phpBB excels in providing powerful group-based permission settings. Forum administrators can create distinct user groups, such as "Management" and "Employees," and then assign specific forum access permissions to these groups. This enables granular control over which users can access which subforums, ensuring that sensitive information remains accessible only to authorized personnel.

Furthermore, phpBB offers a high level of customization in terms of permissions. This means that forum administrators have the flexibility to precisely define what each user group can do within the forum environment. Whether it's controlling access to read, post, upload attachments, or moderate content, phpBB's customizable permissions enable administrators to fine-tune access rights as per their specific requirements.

From a hosting perspective, phpBB is well-supported on various web hosting platforms and can be seamlessly integrated into external servers. Its active community not only provides ongoing support but also offers numerous extensions and styles that further enhance the forum's functionality and appearance.
phpBB is an excellent choice for hosting a closed company forum on external servers due to its efficient user authentication, group-based visibility control, and customizable permissions. The software's comprehensive feature set aligns closely with the specified requirements, making it an optimal solution for your needs.