Merge branch '4.3' into 4.4

* 4.3:
  fix PHP 5.6 compatibility
  [Cache] fixed TagAwareAdapter returning invalid cache
  Add plus character `+` to legal mime subtype
  Make Symfony\Contracts\Service\Test\ServiceLocatorTest abstract
  bug #33942 [DI] Add extra type check to php dumper
  [Dotenv] search variable values in ENV first then env file
  [PropertyInfo] Respect property name case when guessing from public method name
  [VarDumper] fix resetting the "bold" state in CliDumper
  Missing argument in method_exists
  SCA: added missing break in a loop

Author: xabbuh

Dumper/PhpDumper.php

@@ -1953,7 +1953,7 @@ private function isSingleUsePrivateNode(ServiceReferenceGraphNode $node): bool
             if (!$value = $edge->getSourceNode()->getValue()) {
                 continue;
             }
-            if ($edge->isLazy() || !$value->isShared()) {
+            if ($edge->isLazy() || !$value instanceof Definition || !$value->isShared()) {
                 return false;
             }
             $ids[$edge->getSourceNode()->getId()] = true;