Need simple DMS (document management system) or file storage with PHP?

Owncloud will do.
If it is necessary in the browser, try something like joomla. In General, any CMS could be for you. The main thing-precisely to describe the task.
Anyway — one day is not enough. Unless Owncloud

The first thing that came to mind owncloud.org/ is a bit more than required, but maybe additional features will come to the court.

help.zimbra.com/videos/7x/briefcase/
There Are OpenSource

We've done based on WordPress.
For not picky will go out of the box.
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If you need additional functions such as versioning, there is a plugin WPDR, it is still different chips adds.
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This solution has disadvantages, which are continuation of its advantages.
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Key benefits: easily deployed anywhere. Out of the box enough. Can be extended to integrate with anything.
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Has experience in implementing projects such as small companies with 10 employees and offices on 1000 employees distributed network of offices.
Example of project description casepress.org/?portfolio=baza-znanij
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It's not a competitor with ownCloud, rather they are complementary. One of the differences in WP single document can be placed into several folders.
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From minus, if folder a lot, the standard mechanisms are not enough and have to add. In a large project, we've been through. Took out the component and rewrote it so that it worked fine with a large nested folders. It turned out something like Google Drive.