diff --git a/php/src/Google/Protobuf/FieldDescriptor.php b/php/src/Google/Protobuf/FieldDescriptor.php
index 6e5eeca9ff..ac919a24a9 100644
--- a/php/src/Google/Protobuf/FieldDescriptor.php
+++ b/php/src/Google/Protobuf/FieldDescriptor.php
@@ -82,14 +82,6 @@ class FieldDescriptor
         return $this->internal_desc->getType();
     }
 
-    /**
-     * @return int
-     */
-    public function getOneofIndex()
-    {
-        return $this->internal_desc->getOneofIndex();
-    }
-
     /**
      * @return OneofDescriptor
      */
diff --git a/php/src/Google/Protobuf/Internal/Descriptor.php b/php/src/Google/Protobuf/Internal/Descriptor.php
index a965158ebe..02b5433290 100644
--- a/php/src/Google/Protobuf/Internal/Descriptor.php
+++ b/php/src/Google/Protobuf/Internal/Descriptor.php
@@ -193,10 +193,6 @@ class Descriptor
         $desc->setLegacyClass($legacy_classname);
         $desc->setOptions($proto->getOptions());
 
-        foreach ($proto->getField() as $field_proto) {
-            $desc->addField(FieldDescriptor::buildFromProto($field_proto, $desc));
-        }
-
         // Handle nested types.
         foreach ($proto->getNestedType() as $nested_proto) {
             $desc->addNestedType(Descriptor::buildFromProto(
@@ -217,6 +213,11 @@ class Descriptor
             $index++;
         }
 
+        // Pass the descriptor to build FieldDescriptor after the OneofDescriptors are populated.
+        foreach ($proto->getField() as $field_proto) {
+            $desc->addField(FieldDescriptor::buildFromProto($field_proto, $desc));
+        }
+
         return $desc;
     }
 }
diff --git a/php/src/Google/Protobuf/Internal/FieldDescriptor.php b/php/src/Google/Protobuf/Internal/FieldDescriptor.php
index 7ab30dd1c0..875280b75c 100644
--- a/php/src/Google/Protobuf/Internal/FieldDescriptor.php
+++ b/php/src/Google/Protobuf/Internal/FieldDescriptor.php
@@ -49,8 +49,6 @@ class FieldDescriptor
     private $oneof_index = -1;
     private $proto3_optional;
 
-    /** @var Descriptor $containing_type */
-    private $containing_type;
     /** @var OneofDescriptor $containing_oneof */
     private $containing_oneof;
 
@@ -242,10 +240,10 @@ class FieldDescriptor
 
     /**
      * @param FieldDescriptorProto $proto
-     * @param Descriptor $parent_desc
+     * @param Descriptor $desc
      * @return FieldDescriptor
      */
-    public static function getFieldDescriptor($proto, $parent_desc)
+    public static function getFieldDescriptor($proto, $desc)
     {
         $type_name = null;
         $type = $proto->getType();
@@ -261,10 +259,10 @@ class FieldDescriptor
 
         if ($proto->hasOneofIndex()) {
             $oneof_index = $proto->getOneofIndex();
-            $containing_oneof = $parent_desc->getOneofDecl()[$oneof_index];
+            $containing_oneof = $desc->getOneofDecl()[$oneof_index];
         } else {
-            $containing_oneof = null;
             $oneof_index = -1;
+            $containing_oneof = null;
         }
         // TODO: once proto2 is supported, this default should be false
         // for proto2.
@@ -284,7 +282,6 @@ class FieldDescriptor
 
         $field = new FieldDescriptor();
         $field->setName($proto->getName());
-        $field->containing_type = $parent_desc;
         $field->containing_oneof = $containing_oneof;
 
         $json_name = $proto->hasJsonName() ? $proto->getJsonName() :
diff --git a/php/src/Google/Protobuf/Internal/OneofDescriptor.php b/php/src/Google/Protobuf/Internal/OneofDescriptor.php
index e685b26701..a74be1e585 100644
--- a/php/src/Google/Protobuf/Internal/OneofDescriptor.php
+++ b/php/src/Google/Protobuf/Internal/OneofDescriptor.php
@@ -67,7 +67,8 @@ class OneofDescriptor
 
     public function isSynthetic()
     {
-        return count($this->fields) === 1 && $this->fields[0]->getProto3Optional();
+        return !is_null($this->fields) && count($this->fields) === 1
+            && $this->fields[0]->getProto3Optional();
     }
 
     public static function buildFromProto($oneof_proto, $desc, $index)