address review comments

php/src/Google/Protobuf/Internal/Descriptor.php

@@ -163,12 +163,12 @@ class Descriptor
         return $this->legacy_klass;
     }
 
-    public function setPreviouslyReservedClass($klass)
+    public function setPreviouslyUnreservedClass($klass)
     {
         $this->previous_klass = $klass;
     }
 
-    public function getPreviouslyReservedClass()
+    public function getPreviouslyUnreservedClass()
     {
         return $this->previous_klass;
     }
@@ -204,7 +204,7 @@ class Descriptor
         $desc->setFullName($fullname);
         $desc->setClass($classname);
         $desc->setLegacyClass($legacy_classname);
-        $desc->setPreviouslyReservedClass($previous_classname);
+        $desc->setPreviouslyUnreservedClass($previous_classname);
         $desc->setOptions($proto->getOptions());
 
         foreach ($proto->getField() as $field_proto) {

php/src/Google/Protobuf/Internal/DescriptorPool.php

@@ -96,7 +96,7 @@ class DescriptorPool
             $descriptor->getClass();
         $this->class_to_desc[$descriptor->getClass()] = $descriptor;
         $this->class_to_desc[$descriptor->getLegacyClass()] = $descriptor;
-        $this->class_to_desc[$descriptor->getPreviouslyReservedClass()] = $descriptor;
+        $this->class_to_desc[$descriptor->getPreviouslyUnreservedClass()] = $descriptor;
         foreach ($descriptor->getNestedType() as $nested_type) {
             $this->addDescriptor($nested_type);
         }

php/src/Google/Protobuf/Internal/GPBUtil.php

@@ -304,7 +304,7 @@ class GPBUtil
         return "";
     }
 
-    public static function getPreviouslyUnreservedClassNamePrefix(
+    private static function getPreviouslyUnreservedClassNamePrefix(
         $classname,
         $file_proto)
     {
@@ -344,7 +344,7 @@ class GPBUtil
         return implode('\\', $parts);
     }
 
-    public static function getPreviouslyUnreservedClassNameWithoutPackage(
+    private static function getPreviouslyUnreservedClassNameWithoutPackage(
         $name,
         $file_proto)
     {

src/google/protobuf/compiler/php/php_generator.cc

@@ -1330,7 +1330,8 @@ void LegacyReadOnlyGenerateClassFile(const FileDescriptor* file,
         "name", php_namespace);
   }
   std::string newname = FullClassName(desc, options);
-  printer.Print("class_exists(^new^::class);\n",
+  printer.Print("class_exists(^new^::class); // autoload the new class, which "
+      "will also create an alias to the deprecated class\n",
       "new", GeneratedClassNameImpl(desc));
   printer.Print("@trigger_error(__NAMESPACE__ . '\\^old^ is deprecated and will be removed in "
       "the next major release. Use ^fullname^ instead', E_USER_DEPRECATED);\n\n",