(PECL eio >= 0.0.1dev)
eio_symlink — Create a symbolic link
$path
   , string $new_path
   [, int $pri = EIO_PRI_DEFAULT
   [, callable $callback = NULL
   [, mixed $data = NULL
  ]]] )
  eio_symlink() creates a symbolic link
  new_path to path.
  
pathSource path
new_pathTarget path
priThe request priority: EIO_PRI_DEFAULT, EIO_PRI_MIN, EIO_PRI_MAX, or NULL.
If NULL passed, pri internally is set to
EIO_PRI_DEFAULT.
callback
callback function is called when the request is done.
It should match the following prototype: 
void callback(mixed $data, int $result[, resource $req]);
datais custom data passed to the request.
resultrequest-specific result value; basically, the value returned by corresponding system call.
reqis optional request resource which can be used with functions like eio_get_last_error()
data
     Arbitrary variable passed to callback.
     
   eio_symlink() returns request resource on success or FALSE on error.
  
Example #1 eio_symlink() example
<?php
$filename = dirname(__FILE__)."/symlink.dat";
touch($filename);
$link = dirname(__FILE__)."/symlink.link";
function my_symlink_cb($data, $result) {
    global $link, $filename;
    var_dump(file_exists($data) && is_link($data));
    if (!eio_readlink($data, EIO_PRI_DEFAULT, "my_readlink_cb", NULL)) {
        @unlink($link);
        @unlink($filename);
    }
}
function my_readlink_cb($data, $result) {
    global $filename, $link;
    var_dump($result);
    @unlink($link);
    @unlink($filename);
}
eio_symlink($filename, $link, EIO_PRI_DEFAULT, "my_symlink_cb", $link);
eio_event_loop();
?>
The above example will output something similar to:
bool(true) string(16) "/tmp/symlink.dat"