php_stream_seek() repositions the internal
position of stream.
The new position is determined by adding the offset
to the position indicated by whence.
If whence is set to SEEK_SET,
SEEK_CUR or SEEK_END the offset
is relative to the start of the stream, the current position or the end of the stream, respectively.
php_stream_seek() returns 0 on success, but -1 if there was an error.
Note: Not all streams support seeking, although the streams API will emulate a seek if
whenceis set to SEEK_CUR andoffsetis positive, by calling php_stream_read() to read (and discard)offsetbytes.The emulation is only applied when the underlying stream implementation does not support seeking. If the stream is (for example) a file based stream that is wrapping a non-seekable pipe, the streams api will not apply emulation because the file based stream implements a seek operation; the seek will fail and an error result will be returned to the caller.