php man page for stream_set_read_buffer

STREAM_SET_READ_BUFFER(3)						 1						 STREAM_SET_READ_BUFFER(3)

stream_set_read_buffer - Set read file buffering on the given stream

SYNOPSIS
       int stream_set_read_buffer (resource  $stream, int  $buffer)

DESCRIPTION
	Sets the read buffer. It's the equivalent of stream_set_write_buffer(3), but for read operations.

PARAMETERS
	      o $stream
		- The file pointer.

	      o $buffer
		-  The	number	of bytes to buffer. If $buffer is 0 then read operations are unbuffered. This ensures that all reads with fread(3)
		are completed before other processes are allowed to read from that input stream.

RETURN VALUES
	Returns 0 on success, or EOF if the request cannot be honored.

SEE ALSO 
stream_set_write_buffer(3).
PHP Documentation Group 												 STREAM_SET_READ_BUFFER(3)