Implemented Binary Search Tree as Data Structure. Implemented with Iterator Interface.

DIRECTORY.md

@@ -21,6 +21,11 @@
     * [Avltree](./DataStructures/AVLTree/AVLTree.php)
     * [Avltreenode](./DataStructures/AVLTree/AVLTreeNode.php)
     * [Treetraversal](./DataStructures/AVLTree/TreeTraversal.php)
+  * Binarysearchtree
+    * [Binarytreetraversal](./DataStructures/BinarySearchTree/BinaryTreeTraversal.php)
+    * [Bstnode](./DataStructures/BinarySearchTree/BSTNode.php)
+    * [Bstree](./DataStructures/BinarySearchTree/BSTree.php)
+    * [Duplicatekeyexception](./DataStructures/BinarySearchTree/DuplicateKeyException.php)    
   * Disjointsets
     * [Disjointset](./DataStructures/DisjointSets/DisjointSet.php)
     * [Disjointsetnode](./DataStructures/DisjointSets/DisjointSetNode.php)
@@ -131,6 +136,7 @@
     * [Conversionstest](./tests/Conversions/ConversionsTest.php)
   * Datastructures
     * [Avltreetest](./tests/DataStructures/AVLTreeTest.php)
+    * [Bstreetest](./tests/DataStructures/BSTreeTest.php)
     * [Disjointsettest](./tests/DataStructures/DisjointSetTest.php)
     * [Doublylinkedlisttest](./tests/DataStructures/DoublyLinkedListTest.php)
     * [Queuetest](./tests/DataStructures/QueueTest.php)

DataStructures/BinarySearchTree/BSTNode.php

@@ -0,0 +1,66 @@
+<?php
+
+/*
+ * Created by: Ramy-Badr-Ahmed (https://github.com/Ramy-Badr-Ahmed) in Pull Request: #174
+ * https://github.com/TheAlgorithms/PHP/pull/174
+ *
+ * Please mention me (@Ramy-Badr-Ahmed) in any issue or pull request addressing bugs/corrections to this file.
+ * Thank you!
+ */
+
+namespace DataStructures\BinarySearchTree;
+
+class BSTNode
+{
+    public int $key;
+    /**
+     * @var mixed
+     */
+    public $value;
+    public ?BSTNode $left;
+    public ?BSTNode $right;
+    public ?BSTNode $parent;
+
+    /**
+     * @param int $key The key of the node.
+     * @param mixed $value The associated value.
+     */
+    public function __construct(int $key, $value)
+    {
+        $this->key = $key;
+        $this->value = $value;
+        $this->left = null;
+        $this->right = null;
+        $this->parent = null;
+    }
+
+    public function isRoot(): bool
+    {
+        return $this->parent === null;
+    }
+
+    public function isLeaf(): bool
+    {
+        return $this->left === null && $this->right === null;
+    }
+
+    public function getChildren(): array
+    {
+        if ($this->isLeaf()) {
+            return [];
+        }
+
+        $children = [];
+        if ($this->left !== null) {
+            $children['left'] = $this->left;
+        }
+        if ($this->right !== null) {
+            $children['right'] = $this->right;
+        }
+        return $children;
+    }
+    public function getChildrenCount(): int
+    {
+        return count($this->getChildren());
+    }
+}