PSR-7
PSR-7 HTTP message library
...Provides a buffer stream that can be written to fill a buffer, and read from to remove bytes from the buffer. This stream returns a "hwm" metadata value that tells upstream consumers what the configured high water mark of the stream is, or the maximum preferred size of the buffer. The CachingStream is used to allow seeking over previously read bytes on non-seekable streams. This can be useful when transferring a non-seekable entity body fails due to needing to rewind the stream (for example, resulting from a redirect). Data that is read from the remote stream will be buffered in a PHP temp stream so that previously read bytes are cached first in memory, then on disk.