PHP supports the direct io functions as described in the Posix Standard (Section 6) for performing I/O functions at a lower level than the C-Language stream I/O functions (fopen(), fread(),..). The use of the DIO functions should be considered only when direct control of a device is needed. In all other cases, the standard filesystem functions are more than adequate.
Note:
This extension has been moved to the ยป PECL repository and is no longer bundled with PHP as of PHP 5.1.0.
This extension is only available on Windows Platforms as of PHP 5.0.0