diff --git a/php/src/Google/Protobuf/FieldDescriptor.php b/php/src/Google/Protobuf/FieldDescriptor.php
index 6d08cea9da97..ac919a24a97b 100644
--- a/php/src/Google/Protobuf/FieldDescriptor.php
+++ b/php/src/Google/Protobuf/FieldDescriptor.php
@@ -39,6 +39,7 @@ class FieldDescriptor
 {
     use GetPublicDescriptorTrait;
 
+    /** @var  \Google\Protobuf\Internal\FieldDescriptor $internal_desc */
     private $internal_desc;
 
     /**
@@ -81,6 +82,32 @@ public function getType()
         return $this->internal_desc->getType();
     }
 
+    /**
+     * @return OneofDescriptor
+     */
+    public function getContainingOneof()
+    {
+        return $this->getPublicDescriptor($this->internal_desc->getContainingOneof());
+    }
+
+    /**
+     * Gets the field's containing oneof, only if non-synthetic.
+     *
+     * @return null|OneofDescriptor
+     */
+    public function getRealContainingOneof()
+    {
+        return $this->getPublicDescriptor($this->internal_desc->getRealContainingOneof());
+    }
+
+    /**
+     * @return boolean
+     */
+    public function hasOptionalKeyword()
+    {
+        return $this->internal_desc->hasOptionalKeyword();
+    }
+
     /**
      * @return Descriptor Returns a descriptor for the field type if the field type is a message, otherwise throws \Exception
      * @throws \Exception
@@ -114,12 +141,4 @@ public function isMap()
     {
         return $this->internal_desc->isMap();
     }
-
-    /**
-     * @return boolean
-     */
-    public function hasOptionalKeyword()
-    {
-        return $this->internal_desc->hasOptionalKeyword();
-    }
 }
diff --git a/php/src/Google/Protobuf/Internal/FieldDescriptor.php b/php/src/Google/Protobuf/Internal/FieldDescriptor.php
index ce83f63a2b26..3a9a73b729ff 100644
--- a/php/src/Google/Protobuf/Internal/FieldDescriptor.php
+++ b/php/src/Google/Protobuf/Internal/FieldDescriptor.php
@@ -46,8 +46,11 @@ class FieldDescriptor
     private $message_type;
     private $enum_type;
     private $packed;
-    private $is_map;
     private $oneof_index = -1;
+    private $proto3_optional;
+
+    /** @var OneofDescriptor $containing_oneof */
+    private $containing_oneof;
 
     public function __construct()
     {
@@ -169,6 +172,32 @@ public function getPacked()
         return $this->packed;
     }
 
+    public function getProto3Optional()
+    {
+        return $this->proto3_optional;
+    }
+
+    public function setProto3Optional($proto3_optional)
+    {
+        $this->proto3_optional = $proto3_optional;
+    }
+
+    public function getContainingOneof()
+    {
+        return $this->containing_oneof;
+    }
+
+    public function setContainingOneof($containing_oneof)
+    {
+        $this->containing_oneof = $containing_oneof;
+    }
+
+    public function getRealContainingOneof()
+    {
+        return !is_null($this->containing_oneof) && !$this->containing_oneof->isSynthetic()
+            ? $this->containing_oneof : null;
+    }
+
     public function isPackable()
     {
         return $this->isRepeated() && self::isTypePackable($this->type);
@@ -214,6 +243,10 @@ private static function isTypePackable($field_type)
             $field_type !== GPBType::BYTES);
     }
 
+    /**
+     * @param FieldDescriptorProto $proto
+     * @return FieldDescriptor
+     */
     public static function getFieldDescriptor($proto)
     {
         $type_name = null;
@@ -248,8 +281,6 @@ public static function getFieldDescriptor($proto)
         $field = new FieldDescriptor();
         $field->setName($proto->getName());
 
-        $json_name = $proto->hasJsonName() ? $proto->getJsonName() :
-            lcfirst(implode('', array_map('ucwords', explode('_', $proto->getName()))));
         if ($proto->hasJsonName()) {
             $json_name = $proto->getJsonName();
         } else {
@@ -269,6 +300,7 @@ public static function getFieldDescriptor($proto)
         $field->setLabel($proto->getLabel());
         $field->setPacked($packed);
         $field->setOneofIndex($oneof_index);
+        $field->setProto3Optional($proto->getProto3Optional());
 
         // At this time, the message/enum type may have not been added to pool.
         // So we use the type name as place holder and will replace it with the
diff --git a/php/src/Google/Protobuf/Internal/OneofDescriptor.php b/php/src/Google/Protobuf/Internal/OneofDescriptor.php
index 67b107f6a4b6..432368571023 100644
--- a/php/src/Google/Protobuf/Internal/OneofDescriptor.php
+++ b/php/src/Google/Protobuf/Internal/OneofDescriptor.php
@@ -37,6 +37,7 @@ class OneofDescriptor
     use HasPublicDescriptorTrait;
 
     private $name;
+    /** @var \Google\Protobuf\FieldDescriptor[] $fields */
     private $fields;
 
     public function __construct()
@@ -64,13 +65,21 @@ public function getFields()
         return $this->fields;
     }
 
+    public function isSynthetic()
+    {
+        return !is_null($this->fields) && count($this->fields) === 1
+            && $this->fields[0]->getProto3Optional();
+    }
+
     public static function buildFromProto($oneof_proto, $desc, $index)
     {
         $oneof = new OneofDescriptor();
         $oneof->setName($oneof_proto->getName());
         foreach ($desc->getField() as $field) {
+            /** @var FieldDescriptor $field */
             if ($field->getOneofIndex() == $index) {
                 $oneof->addField($field);
+                $field->setContainingOneof($oneof);
             }
         }
         return $oneof;
diff --git a/php/src/Google/Protobuf/OneofDescriptor.php b/php/src/Google/Protobuf/OneofDescriptor.php
index 92b4e279dac3..66ffbd5caf9d 100644
--- a/php/src/Google/Protobuf/OneofDescriptor.php
+++ b/php/src/Google/Protobuf/OneofDescriptor.php
@@ -38,6 +38,7 @@ class OneofDescriptor
 {
     use GetPublicDescriptorTrait;
 
+    /** @var  \Google\Protobuf\Internal\OneofDescriptor $internal_desc */
     private $internal_desc;
 
     /**
@@ -62,6 +63,12 @@ public function getName()
      */
     public function getField($index)
     {
+        if (
+            is_null($this->internal_desc->getFields())
+            || !isset($this->internal_desc->getFields()[$index])
+        ) {
+            return null;
+        }
         return $this->getPublicDescriptor($this->internal_desc->getFields()[$index]);
     }
 
@@ -75,6 +82,6 @@ public function getFieldCount()
 
     public function isSynthetic()
     {
-      return $this->internal_desc->isSynthetic();
+        return $this->internal_desc->isSynthetic();
     }
 }