<?php
 
function recusive_list($items) {
	$html = '<ul>';
	foreach ($items as $item) {
		$html .= '<li>';
		$html .= '<a target="_blank" href="' .$item['href']. '">' .$item['name']. '</a>';
		$html .= recusive_list($item['childs']). '</li>';
	}
	$html .= '</ul>';
	return $html;
}
 
$items = [
	[
		'href' => 'www.item1',
		'name' => 'Item1',
		'childs' => [
			[
				'href' => 'www.item1.1',
				'name' => 'Item1.1',
				'childs' => []
			]
		]
	],
	[
		'href' => 'www.item2',
		'name' => 'Item2',
		'childs' => [
			[
				'href' => 'www.item2.1',
				'name' => 'Item2.1',
				'childs' => [
					[
						'href' => 'www.item2.1.1',
						'name' => 'Item2.1.1',
						'childs' => []
					],
					[
						'href' => 'www.item2.1.2',
						'name' => 'Item2.1.2',
						'childs' => [
							[
								'href' => 'www.item2.1.2.1',
								'name' => 'Item2.1.2.1',
								'childs' => []
							]
						]
					]
				]
			]
		]
	],
	[
		'href' => 'www.item3',
		'name' => 'Item3',
		'childs' => []
	],
];
 
echo recusive_list($items);

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