Convert flat array to the multi-dimensional

Question

I have an array with tree data (by parent id). I want to convert it to multidimensional array. What is the best way to achieve that? Is there any short function for that?

Answer 1

I was looking for an example of how to do this, with categories. This example assumes that parents will always have a parent id of '0'. The example is using ZF2.

No references, or recursion. The trick is in the output, you look for the [0] index, and for the children, you specify the parent_id as the index.

$categoryLookup = $this->getCategoryLookup($associateById=true);

if ($assignedCategories) {          
    $categoryHeirarchy = array();
    foreach($assignedCategories as $assignedCategory) {
        $child = $categoryLookup[$assignedCategory->category_id];
        $parent = $categoryLookup[$child->parent_id];               
        $categoryHeirarchy[$child->parent_id][] = $categoryLookup[$child->category_id];
        $categoryHeirarchy[$parent->parent_id][$parent->category_id] = $categoryLookup[$parent->category_id];
    }           

    return $categoryHeirarchy;  
}


Categories

    categoryHeirarchy[0] as $parent): ?>
        
escapeHtml($parent->name); ?>
        categoryHeirarchy[$parent->category_id] as $child): ?>
            
escapeHtml($child->name); ?>