fix: fix PHP readonly legacy files for nested messages
diff --git a/php/tests/GeneratedClassTest.php b/php/tests/GeneratedClassTest.php
index 37c33df..b42649d 100644
--- a/php/tests/GeneratedClassTest.php
+++ b/php/tests/GeneratedClassTest.php
@@ -338,6 +338,7 @@
     {
         $this->assertTrue(class_exists('\Upper\READONLY'));
         $this->assertTrue(class_exists('\Lower\readonly'));
+        $this->assertTrue(class_exists('\Php\Test\TestNamespace\PBEmpty\ReadOnly'));
     }
 
     public function testLegacyReadOnlyEnum()