Added some other checks

Author: lazychaser

README.markdown

@@ -327,6 +327,12 @@ To check whether the node is root:
 $bool = $node->isRoot();
 ```
 
+Other checks:
+
+*   `$node->isChildOf($other);`
+*   `$node->isAncestorOf($other);`
+*   `$node->isSiblingOf($other);`
+
 ### Checking consistency
 
 You can check whether a tree is broken (i.e. has some structural errors):

src/Kalnoy/Nestedset/Node.php

@@ -1035,6 +1035,42 @@ public function isDescendantOf(Node $other)
         return $this->getLft() > $other->getLft() and $this->getLft() < $other->getRgt();
     }
 
+    /**
+     * Get whether the node is immediate children of other node.
+     *
+     * @param Node $other
+     *
+     * @return bool
+     */
+    public function isChildOf(Node $other)
+    {
+        return $this->getParentId() == $other->getKey();
+    }
+
+    /**
+     * Get whether the node is a sibling of another node.
+     *
+     * @param Node $other
+     *
+     * @return bool
+     */
+    public function isSiblingOf(Node $other)
+    {
+        return $this->getParentId() == $other->getParentId();
+    }
+
+    /**
+     * Get whether the node is an ancestor of other node, including immediate parent.
+     *
+     * @param Node $other
+     *
+     * @return bool
+     */
+    public function isAncestorOf(Node $other)
+    {
+        return $other->isDescendantOf($this);
+    }
+
     /**
      * Get statistics of errors of the tree.
      *