clarification added (#19220)

framework/web/CookieCollection.php

@@ -106,7 +106,7 @@ class CookieCollection extends BaseObject implements \IteratorAggregate, \ArrayA
 
     /**
      * Returns whether there is a cookie with the specified name.
-     * Note that if a cookie is marked for deletion from browser, this method will return false.
+     * Note that if a cookie is marked for deletion from browser or its value is an empty string, this method will return false.
      * @param string $name the cookie name
      * @return bool whether the named cookie exists
      * @see remove()