How to perform filesystem operations in transaction with php?

Question

I am looking for ways to implement filesystem operations using php with transaction support. Like if I am performing operations like move, copy and delete inside a transaction, if one of them fails, the script needs to revert all those operations already performed. I am kind of clueless and am seeking guidance how it can be achieved. And if available libraries or solutions exists? I apologize if the question sounds vague.

Answer 1

The most common pattern for this is copying everything to somewhere else, operate on the copy and replace the originals if everything goes right.

Something tells me that PHP stream wrappers could be useful for this as well. It is possible to override the 'file://' protocol and operate in a virtual filesystem (proof of concept: https://github.com/Respect/Test#streamwrapper).

Answer 2

Filesystems - in contrast to database management systems - do not support transactions. However some do provide the things you need to implement transactions; that is locking and logging. Logging will not be your problem because you can do it in php, too, but you'll need a filesystem that provides file locks.

I recommend you not to implement anything like this youself - there are lot of problems you might encounter. The database guys look back on a research history of decades, here.

But if you have to, you could (for a start) implement something like Two-phase locking in php. Also, you might consider using the command pattern, that helps with undo functionality for your rollback.