以下是一个PHP无限分级实例，我们将使用递归函数来构建一个无限深的层级结构。这个例子中，我们将创建一个简单的目录结构，每个目录可以包含子目录。
```php
// 定义一个目录结构数组
$directory_structure = [
'root' => [
'name' => 'Root',
'children' => [
'dir1' => [
'name' => 'Directory 1',
'children' => [
'dir1_1' => [
'name' => 'Directory 1.1',
'children' => [
'dir1_1_1' => [
'name' => 'Directory 1.1.1',
'children' => []
]
]
]
]
],
'dir2' => [
'name' => 'Directory 2',
'children' => [
'dir2_1' => [
'name' => 'Directory 2.1',
'children' => []
]
]
]
]
]
];
// 递归函数来打印目录结构
function printDirectoryStructure($directory, $indent = 0) {
echo str_repeat(' ', $indent) . $directory['name'] . "
