How to get equal columns? – SEO

I have this class for a megamenu used in a category menu for an ecommerce web application.

class categories {

    var $categorie;
    var $tabs;
    var $subcategorie;
    var $website;

    var $coloane = 3;
    var $randuri = 10;


    function tabs(){

        global $pdoconnect;

        $stmt =  $pdoconnect->query("SELECT * FROM taburi WHERE vizibil = '1' ORDER BY ordine ASC");
        $tabs = $stmt->fetchAll(PDO::FETCH_ASSOC);
        $tabs_c = $stmt->rowCount();

        $return = "";
        if($tabs_c > 0){
            $i = 1;
            $return .= "n<ul class="tabs">n";
            foreach($tabs as $t){
                $return .= "t<li class="level0">n";
                $return .= "tt<div class="tab-title">n";
                $return .= "ttt<span class="tab-image">n";
                $return .= "tttt".'<img src="'.$this->website.'/media/taburi/'.$t['logo'].'" />'."n";
                $return .= "ttt</span>n";
                $return .= $t['nume'];
                $return .= "tt</div>n";
                $return .= "t".'<div class="level1 hmm-megamenu-box">'."n";
                $return .= $this->categorie($t['id']);
                $return .= "t</div>n";
                $return .= "t</li>n";
            }
            $return .= "</ul>";
        }
        return  $return;
    }

    function categorie($tab){
        global $pdoconnect;

        $return = "";
        $stmt = $pdoconnect->prepare("SELECT * FROM categorii WHERE tab =:tab AND vizibil='1'");
        $stmt->bindValue(':tab', $tab, PDO::PARAM_INT);
        $stmt->execute();

        $categorie   = $stmt->fetchAll(PDO::FETCH_ASSOC);
        $categorie_c = $stmt->rowCount();

        if($categorie_c > 0){
            $i = 0;
            $return .= "<div class="hmm-megamenu-block">n";
            foreach ($categorie as $cat) {
                $return .= "t<div class="hmm-megamenu-column">n";
                // if($i % 2 == 0 && !empty($i) && $this->countSubcategorii($cat['categorie']) <= $this->randuri){
                //  $return .= "</div><div class="hmm-megamenu-column">n";
                // }
                $return .= "ttt<a class="head-list">".$cat['categorie']."<i class="fa fa-chevron-right" style="font-size: 8px; margin-left: 5px;"></i></a>n";
                $return .= $this->subcategorie($cat['categorie']);
                $return .= "tt</div>n";
                $i++;
            }

            $return .= "</div>";

        }
        return $return;

    }


    function subcategorie($cat){
        global $pdoconnect;

        $return = "";
        $stmt = $pdoconnect->prepare("SELECT * FROM categorii WHERE categorie=:categorie AND subcategorie IS NOT NULL");
        $stmt->bindValue(':categorie', $cat, PDO::PARAM_STR);
        $stmt->execute();

        $subcategorie = $stmt->fetchAll(PDO::FETCH_ASSOC);

        $subcategorie_c = $stmt->rowCount();

        if($subcategorie_c > 0){
            foreach ($subcategorie as $scat) {
                $return .= "t".'<a href="'.$this->website.'/c/'.strtolower($scat['seo']).'">'.$scat['subcategorie'].'</a>'."n";
            }
        }
        return $return;
    }
}

For the moment the menu items looks like this

but the desired result should be

How can i get this result just with php?