This extension provides interface to the libeio library.

Libeio is a an asynchronous I/O library. Features basically include
asynchronous versions of POSIX API(read, write, open, close, stat, unlink,
fdatasync, mknod, readdir etc.); sendfile (native on Solaris, Linux, HP-UX,
FreeBSD); readahead. libeio itself emulates the system calls, if they are not
available on specific(UNIX-like) platform.

WWW: http://pecl.php.net/package/eio/