Merge branch '3.4' into 4.3

* 3.4:
  [DoctrineBridge] try to fix deprecations from doctrine/persistence
  [Translation] fix memoryleak in PhpFileLoader

Loader/PhpFileLoader.php

@@ -18,11 +18,25 @@
  */
 class PhpFileLoader extends FileLoader
 {
+    private static $cache = [];
+
     /**
      * {@inheritdoc}
      */
     protected function loadResource($resource)
     {
-        return require $resource;
+        if ([] === self::$cache && \function_exists('opcache_invalidate') && filter_var(ini_get('opcache.enable'), FILTER_VALIDATE_BOOLEAN) && (!\in_array(\PHP_SAPI, ['cli', 'phpdbg'], true) || filter_var(ini_get('opcache.enable_cli'), FILTER_VALIDATE_BOOLEAN))) {
+            self::$cache = null;
+        }
+
+        if (null === self::$cache) {
+            return require $resource;
+        }
+
+        if (isset(self::$cache[$resource])) {
+            return self::$cache[$resource];
+        }
+
+        return self::$cache[$resource] = require $resource;
     }
 }