<?php
// Create a directory recursively (make sure to sanitize if taken from input as always!)
mkdir("/path/to/my/dir", 0777, true);
<?php
// Desired directory structure
$structure = './depth1/depth2/depth3/';
// To create the nested structure, the $recursive parameter
// to mkdir() must be specified.
if (!mkdir($structure, 0777, true)) {
die('Failed to create directories...');
}