Fixed some phpstan errors

src/Group/ConnectionGroup.php

@@ -46,11 +46,19 @@ class ConnectionGroup implements EventEmitterInterface, IteratorAggregate, Count
         return count($this->connections);
     }
 
+    /** 
+     * 
+     * @return \Traversable<int,WebSocketInterface> 
+     */
     public function getIterator(): Traversable
     {
         return new ArrayIterator($this->connections);
     }
 
+    /**
+     * 
+     * @return WebSocketInterface[]
+     */
     public function getAll(): array
     {
         return $this->connections;
@@ -70,6 +78,10 @@ class ConnectionGroup implements EventEmitterInterface, IteratorAggregate, Count
         }
     }
 
+    /**
+     * 
+     * @return void
+     */
     public function closeAll(string $reason, int $code=1001)
     {
         foreach ($this->connections as $connection) {