Update the PHPDoc.

src/Node/KeyValueNode.php

@@ -5,12 +5,14 @@
 namespace drupol\phptree\Node;
 
 /**
- * Class Node
+ * Class KeyValueNode
  */
 class KeyValueNode extends ValueNode implements KeyValueNodeInterface
 {
     /**
-     * @var mixed|null
+     * The key property.
+     *
+     * @var string|mixed|int|null
      */
     private $key;
 

src/Node/KeyValueNodeInterface.php

@@ -5,12 +5,15 @@
 namespace drupol\phptree\Node;
 
 /**
- * Class KeyValueNodeInterface
+ * Interface KeyValueNodeInterface
  */
 interface KeyValueNodeInterface extends ValueNodeInterface
 {
     /**
+     * Get the node key.
+     *
      * @return string|mixed|int|null
+     *   The key value.
      */
     public function getKey();
 }

src/Node/Node.php

@@ -10,6 +10,8 @@
 class Node implements NodeInterface
 {
     /**
+     * The storage property.
+     *
      * @var array
      */
     protected $storage;
@@ -75,7 +77,7 @@ public function getParent(): ?NodeInterface
     /**
      * {@inheritdoc}
      */
-    public function children():array
+    public function children(): array
     {
         return $this->storage['children'];
     }
@@ -139,7 +141,7 @@ function ($child) use ($node) {
     /**
      * {@inheritdoc}
      */
-    public function degree():int
+    public function degree(): int
     {
         return \count($this->storage['children']);
     }

src/Node/NodeInterface.php

@@ -5,63 +5,96 @@
 namespace drupol\phptree\Node;
 
 /**
- * Class NodeInterface
+ * Interface NodeInterface
  */
 interface NodeInterface extends \Countable
 {
     /**
-     * @return \drupol\phptree\Node\NodeInterface|null
+     * Get the parent node.
+     *
+     * @return NodeInterface|null
+     *   The parent node if any, null otherwise.
      */
     public function getParent(): ?NodeInterface;
 
     /**
-     * @param \drupol\phptree\Node\NodeInterface $node
+     * Set the parent.
+     *
+     * @param NodeInterface $node
+     *   The parent node.
      *
-     * @return \drupol\phptree\Node\NodeInterface
+     * @return NodeInterface
+     *   The node.
      */
     public function setParent(NodeInterface $node): NodeInterface;
 
     /**
-     * @param \drupol\phptree\Node\NodeInterface ...$node
+     * The node to add.
+     *
+     * @param NodeInterface ...$node
+     *   The node to add.
      *
-     * @return \drupol\phptree\Node\NodeInterface
+     * @return NodeInterface
+     *   The node.
      */
     public function add(NodeInterface ...$node): NodeInterface;
 
     /**
-     * @param \drupol\phptree\Node\NodeInterface ...$node
+     * Remove children.
      *
-     * @return \drupol\phptree\Node\NodeInterface
+     * @param NodeInterface ...$node
+     *   The node to remove.
+     *
+     * @return NodeInterface
+     *   The node.
      */
     public function remove(NodeInterface ...$node): NodeInterface;
 
     /**
+     * Get the children.
+     *
      * @return NodeInterface[]
+     *   The children.
      */
     public function children(): array;
 
     /**
+     * Check if the node is a leaf.
+     *
      * @return bool
+     *   True if it's a leaf, false otherwise.
      */
     public function isLeaf(): bool;
 
     /**
+     * Check if the node is the root node.
+     *
      * @return bool
+     *   True if it's a root node, false otherwise.
      */
     public function isRoot(): bool;
 
     /**
-     * @return array
+     * Get the ancestors of a node.
+     *
+     * @return NodeInterface[]
+     *   The array of ancestors.
      */
     public function getAncestors(): array;
 
     /**
-     * @return array
+     * Get the node's sibblings.
+     *
+     * @return NodeInterface[]
+     *   The array of sibblings.
      */
     public function getSibblings(): array;
 
     /**
+     * The number of children a node has.
+     *
      * @return int
+     *   The amound of children.
      */
     public function degree(): int;
 }

src/Node/ValueNode.php

@@ -10,7 +10,7 @@
 class ValueNode extends Node implements ValueNodeInterface
 {
     /**
-     * @var mixed|null
+     * @var string|mixed|null
      */
     private $value;
 

src/Node/ValueNodeInterface.php

@@ -5,12 +5,15 @@
 namespace drupol\phptree\Node;
 
 /**
- * Class ValueNodeInterface
+ * Interface ValueNodeInterface
  */
 interface ValueNodeInterface extends NodeInterface
 {
     /**
+     * Get the node value.
+     *
      * @return string|mixed|null
+     *   The node value.
      */
     public function getValue();
 }

src/Visitor/AbstractVisitor.php

@@ -4,12 +4,13 @@
 
 use drupol\phptree\Node\NodeInterface;
 
-abstract class AbstractVisitor
+/**
+ * Class AbstractVisitor
+ */
+abstract class AbstractVisitor implements VisitorInterface
 {
     /**
-     * @param \drupol\phptree\Node\NodeInterface $node
-     *
-     * @return \Traversable
+     * {@inheritdoc}
      */
     abstract public function traverse(NodeInterface $node): \Traversable;
 }

src/Visitor/VisitorInterface.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace drupol\phptree\Visitor;
+
+use drupol\phptree\Node\NodeInterface;
+
+/**
+ * Interface VisitorInterface
+ */
+interface VisitorInterface
+{
+    /**
+     * Traverse the tree.
+     *
+     * @param \drupol\phptree\Node\NodeInterface $node
+     *   The node.
+     *
+     * @return \Traversable
+     */
+    public function traverse(NodeInterface $node): \Traversable;
+}