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() 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.