Get menu array from HTML string using PHP DOM document

I have the following code:

$string = '<html><head></head><body><ul id="mainmenu">
  <li id="1"><a href="1"> main menu 1 </a> </li>
  <li id="2"> <a href="2"> main menu 2 </a> </li>
    <ul class="sub-menu">
      <li id="3"> <a href="3"> Sub menu 2 </a> </li>
      <li id="4"> <a href="4"> Sub menu 2.1 </a> </li>
    </ul>
  </li>
</ul></body></html>';
$dom = new DOMDocument;
$dom->loadHTML($string);

Now I want an array as output containing href, value and submenu fields with respective values using PHP DOM document.

Something like this:

Array
(
    [0] => Array
        (
            [href] => 1
            [name] => Main menu 1
            [sub] => Array
                (
                )

        )

    [1] => Array
        (
            [href] => 2
            [name] => main menu 2
            [sub] => Array
                (
                   [0] => Array
                    (
                       [href] => 3
                       [name] => sub menu 2
                       [sub] => Array
                             (
                              )

                    )

                   [1] => Array
                       (
                         [href] => 4
                          [name] => sub main menu 2.1
                         [sub] => Array
                             (

                             )

                   )
                )

        )
)

I am able to get all the menu items as main menu and all submenu array as empty. How can I achieve this by parsing HTML string?

Solution

Assuming that you just have the two levels, this code uses XPath to find the start of each menu and then loops through the <li> elements. It does a similar thing for the sub menus, using the current main menu as the start point and only the contents (using descendant:: to limit the nodes searched)....

(I've had to alter the HTML as there was an extra <li> in <li id="2"> <a href="2"> main menu 2 </a> </li>)

$string = '<html><head></head><body><ul id="mainmenu">
  <li id="1"><a href="1"> main menu 1 </a> </li>
  <li id="2"> <a href="2"> main menu 2 </a>
    <ul class="sub-menu">
      <li id="3"> <a href="3"> Sub menu 2 </a> </li>
      <li id="4"> <a href="4"> Sub menu 2.1 </a> </li>
    </ul>
  </li>
</ul></body></html>';
$dom = new DOMDocument;
$dom->loadHTML($string);
$xp = new DOMXPath($dom);
$menus = [];

$mainMenus = $xp->query('//ul[@id="mainmenu"]/li');
foreach ( $mainMenus as $menu )  {
    $a = $menu->getElementsByTagName("a")[0];
    $newMenu = [ "href" => $a->getAttribute("href"),
        "name" => $a->textContent
    ];

    $subMenus = $xp->query('descendant::ul[@class="sub-menu"]/li', $menu);
    foreach ( $subMenus as $menu1 )  {
        $a = $menu1->getElementsByTagName("a")[0];

        $newMenu['sub'][] = [ "href" => $a->getAttribute("href"),
            "name" => $a->textContent
        ];
    }
    $menus[] = $newMenu;
}

If you have a list of possible ID's, then you could use the XPath to find any of them..

//ul[@id="mainmenu" or @id="menu-main" or @id="menu-menu1"]/li

You could build this dynamically from an array if you need to...

$menu_ids_arr = array('mainmenu', 'menu-main', 'menu-menu1');
$query = '//ul[';
foreach ( $menu_ids_arr as $id )    {
    $query .= '@id="'.$id.'" or ';
}
$query = substr($query, 0, -4).']/li';
$mainMenus = $xp->query($query);