Added example of Tail recursion : building a nested category tree

Author: Alienpruts

chap-05/category-tree-recursive.php

@@ -0,0 +1,36 @@
+<?php
+/**
+ * Created by PhpStorm.
+ * User: bert
+ * Date: 4/10/18
+ * Time: 15:17
+ */
+
+$array = [
+    ["id" => 1, "categoryName" => "First", "parentCategory" => 0, "SortInd" => 0],
+    ["id" => 2, "categoryName" => "Second", "parentCategory" => 1, "SortInd" => 0],
+    ["id" => 3, "categoryName" => "Third", "parentCategory" => 1, "SortInd" => 1],
+    ["id" => 4, "categoryName" => "Fourth", "parentCategory" => 3, "SortInd" => 0],
+    ["id" => 5, "categoryName" => "Fifth", "parentCategory" => 4, "SortInd" => 0],
+    ["id" => 6, "categoryName" => "Sixth", "parentCategory" => 5, "SortInd" => 0],
+    ["id" => 7, "categoryName" => "Seventh", "parentCategory" => 6, "SortInd" => 0],
+    ["id" => 8, "categoryName" => "Eight", "parentCategory" => 7, "SortInd" => 0],
+    ["id" => 9, "categoryName" => "Ninth", "parentCategory" => 1, "SortInd" => 0],
+    ["id" => 10, "categoryName" => "Tenth", "parentCategory" => 2, "SortInd" => 1],
+];
+
+foreach ($array as $row){
+    $categories[$row["parentCategory"]][] = $row;
+}
+
+showCategoryTree($categories, 0);
+
+function showCategoryTree(array $categories, int $n) {
+    if (isset($categories[$n])) {
+        foreach ($categories[$n] as $category) {
+            echo str_repeat("-", $n) . "" . $category["categoryName"] . PHP_EOL;
+            showCategoryTree($categories, $category["id"]);
+        }
+    }
+    return;
+}