array_multisort() php array function

How to use array_multisort() function in an array in php language.I am explain array_multisort() use for php function.

array_multisort() :-

Definition & Usage :- The array_multisort() function Sorts multiple or multidimensional arrays.

<?php
$a = array('red', 'black', 'apple'); 
array_multisort($a); 
print_r($a);
?> 
output//
array( [0] => apple [1] => black [2] => red)