tree

<?php

$tree = [
    [
        "id" => "1",
        "name" => "test 1",
        "parent" => null,
        "_children" => [
            [
                "id" => "1.1",
                "name" => "test 1.1",
                "parent" => "1",
                "_children" => [
                    [
                        "id" => "1.1.1",
                        "parent" => "1.1",
                        "name" => "test 1.1.1"
                    ],
                    [
                        "id" => "1.1.2",
                        "parent" => "1.1",
                        "name" => "test 1.2"
                    ],
                    [
                        "id" => "1.1.3",
                        "parent" => "1.1",
                        "name" => "test 1.3"
                    ]
                ]
            ],
            [
                "id" => "1.2",
                "parent" => "1",
                "name" => "test 1.2"
            ],
            [
                "id" => "1.3",
                "parent" => "1",
                "name" => "test 1.3"
            ],
            [
                "id" => "1.4",
                "parent" => "1",
                "name" => "test 1.4"
            ]
        ]
    ],
    [
        "id" => "2",
        "name" => "test 2",
        "parent" => null,
        "_children" => [
            [
                "id" => "2.1",
                "parent" => "2",
                "name" => "test 2.1"
            ],
            [
                "id" => "2.2",
                "parent" => "2",
                "name" => "test 2.2"
            ],
            [
                "id" => "2.3",
                "parent" => "2",
                "name" => "test 2.3"
            ],
            [
                "id" => "2.4",
                "parent" => "2",
                "name" => "test 2.4"
            ]
        ]
    ],
    [
        "id" => "3",
        "name" => "test 3",
        "parent" => null,
    ]
];

function printTree($tree, $parent = null)
{
    $has_children = false;

    foreach ($tree as $element) {
        if ($element["parent"] == $parent) {
            echo $element["id"] . " => " . $element["name"];
            if (isset($element["_children"])) {
                $has_children = true;
                echo "<div class='children'>";
                printTree($element["_children"], $element["id"]);
                echo "</div>";            }
        }
    }

    if($has_children){
        echo "</div>";
    }
}

printTree($tree);