具有HTML树级别的PHP数组

echo nestedHtmlList($array);

function nestedHtmlList($array) {
    $depth = 0;
    $result = "";
    foreach ($array as $node) {
        $newDepth = $node[1];

        if ($newDepth > $depth) {
            $result .= "<ul><li>";
        } else if ($newDepth < $depth) {
            for ($d = $newDepth; $d < $depth; $d++) {
                $result .= "</li></ul>";
            }
            $result .= "</li><li>";
        } else if ($result == "") {
            $result .= "<ul><li>";
        } else {
            $result .= "</li><li>";
        }
        $result .= "<input type='checkbox' /><span>";
        $result .= $node[0];
        $result .= "</span>";

        $depth = $newDepth;
    }

    while ($depth > 0) {
        $result .= "</li></ul>";
        $depth -= 1;
    }

    return $result;
}

$array = [];
$array[0][0]="Node 1";
$array[0][1]=0;
$array[1][0]="Node 2";
$array[1][1]=0;
$array[2][0]="Node 2.1";
$array[2][1]=1;
$array[3][0]="Node 2.1.1";
$array[3][1]=2;
$array[4][0]="Node 2.2";
$array[4][1]=1;

function makeList( &$array, $level = null ) {
    $html = '<ul>';
    $html .= '<li>Level: ' . $level;
    while( $element = array_shift( $array ) ) {
        if( $level == $element[1] ) {
            $html .= '</li><li><label><input type="checkbox"/> ' . $element[0] . '</label>';
        } else if( $level < $element[1] ) {
            array_unshift( $array, $element );
            $html .= makeList( $array, $element[1] ) . '</li>';
        } else {
            array_unshift( $array, $element );
            break;
        }
    }
    $html .= '</ul>';

    return $html;
}

echo '<pre>';
echo makeList($array);

Level: 
[] Node 1
[] Node 2
Level: 1
    [] Node 2.1
    Level: 2
        [] Node 2.1.1
    [] Node 2.2