How Can I Build a Hierarchical Tree Structure in PHP from Parent-Child Relationships?

Hierarchical Tree Structure Creation from Parent-Child Relationships

Constructing hierarchical tree structures from parent-child relationships is a common task in programming. To achieve this, a recursive approach can be employed, effectively organizing the data into nested units.

In PHP, converting a series of parent-child pairs into a hierarchical tree requires two key functions: parsing and printing. The parsing function systematically traverses the child-parent pairs to build a hierarchical data structure. Following this, the printing function converts this structure into a series of nested HTML unordered lists, with each list item representing a child.

As an example, consider the following parent-child pairs:

Child : Parent
H : G
F : G
G : D
E : D
A : E
B : C
C : E
D : NULL

To parse this data, we define the parseTree function:

function parseTree($tree, $root = null) {
    $return = array();
    foreach($tree as $child => $parent) {
        if($parent == $root) {
            unset($tree[$child]);
            $return[] = array(
                'name' => $child,
                'children' => parseTree($tree, $child)
            );
        }
    }
    return empty($return) ? null : $return;
}

Next, we define the printTree function to convert the parsed hierarchy into HTML unordered lists:

function printTree($tree) {
    if(!is_null($tree) && count($tree) > 0) {
        echo '<ul>';
        foreach($tree as $node) {
            echo '<li>'.$node['name'];
            printTree($node['children']);
            echo '</li>';
        }
        echo '</ul>';
    }
}

By combining these two functions, we can successfully convert child-parent pairs into hierarchical tree structures.

The above is the detailed content of How Can I Build a Hierarchical Tree Structure in PHP from Parent-Child Relationships?. For more information, please follow other related articles on the PHP Chinese website!