(PHP 5 >= 5.3.3)
stream_set_read_buffer — Set read file buffering on the given stream
$stream
   , int $buffer
   )Sets the read buffer. It's the equivalent of stream_set_write_buffer(), but for read operations.
streamThe file pointer.
buffer
      The number of bytes to buffer. If buffer
      is 0 then read operations are unbuffered.  This ensures that all reads
      with fread() are completed before other processes are
      allowed to read from that input stream.
     
Returns 0 on success, or another value if the request cannot be honored.