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 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