In its simplest definition, a stream is a resource object which exhibits streamable behavior.
Streams were introduced with PHP 4.3.0 as a way of generalizing file, network, data compression, and other opperations which share a common set of functions and uses. In its simplest definition, a stream is a resource object which exhibits streamable behavior. That is, it can be read from or written to in a linear fashion, and may be able to fseek() to an arbitrary locations within the stream.