Update syntax.

src/Node/Node.php

@@ -159,11 +159,9 @@ public function withChildren(NodeInterface ...$nodes): NodeInterface
         $clone = clone $this;
         $clone->storage['children'] = [];
 
-        foreach ($nodes as $node) {
-            $clone->add($node);
-        }
-
-        return $clone;
+        return [] === $nodes ?
+            $clone:
+            $clone->add(...$nodes);
     }
 
     /**

src/Node/NodeInterface.php

@@ -94,7 +94,7 @@ public function getSibblings(): \Traversable;
      * The number of children a node has.
      *
      * @return int
-     *   The amound of children.
+     *   The amount of children.
      */
     public function degree(): int;
 
@@ -105,4 +105,15 @@ public function degree(): int;
      *   The depth is the number of nodes before root.
      */
     public function depth(): int;
+
+    /**
+     * Get a clone of the object without any children.
+     *
+     * @param \drupol\phptree\Node\NodeInterface ...$nodes
+     *   The children that the clone will have.
+     *
+     * @return \drupol\phptree\Node\NodeInterface
+     *   The new object.
+     */
+    public function withChildren(NodeInterface ...$nodes): NodeInterface;
 }