Implemented Binary Search Tree Data Structure with Iterator.

DataStructures/BinarySearchTree/BSTNode.php

@@ -1,14 +1,66 @@
 <?php
 
 /*
- * Created by: Ramy-Badr-Ahmed (https://github.com/Ramy-Badr-Ahmed) in Pull Request: #173
- * https://github.com/TheAlgorithms/PHP/pull/173
+ * 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());
+    }
+}