Sergey Zhuk has posted another ReactPHP tutorial to his site, this time focusing on working with the filesystem from a ReactPHP application.

I/O operations in the filesystem are often very slow, compared with CPU calculations. In an asynchronous PHP application this means that every time we access the filesystem even with a simple fopen() call, the event loop is being blocked. All other operations cannot be executed while we are reading or writing on the disk.

[...] So, what is the solution? ReactPHP ecosystem already has a component that allows you to work asynchronously with a filesystem: reactphp/filesystem. This component provides a promise-based interface for the most commonly used operations within a filesystem.

He starts the code with a bit of setup, creating the initial event loop, the related Filesystem instance and a pointer to a "test.txt" file. He then walks through the basic filesystem operations and the code required: reading in the file contents, creating a new file and writing content back out to a file. The next section goes through the same functionality for directories. He ends the post with a look at symbolic link creation, read and delete operations.