diff --git a/php/src/Google/Protobuf/FieldDescriptor.php b/php/src/Google/Protobuf/FieldDescriptor.php
index 6d08cea9da..128f0f08bd 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 +82,22 @@ class FieldDescriptor
         return $this->internal_desc->getType();
     }
 
+    /**
+     * @return int
+     */
+    public function getOneofIndex()
+    {
+        return $this->internal_desc->getOneofIndex();
+    }
+
+    /**
+     * @return boolean
+     */
+    public function getProto3Optional()
+    {
+        return $this->internal_desc->getProto3Optional();
+    }
+
     /**
      * @return Descriptor Returns a descriptor for the field type if the field type is a message, otherwise throws \Exception
      * @throws \Exception
@@ -114,12 +131,4 @@ class FieldDescriptor
     {
         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 ce83f63a2b..368797b340 100644
--- a/php/src/Google/Protobuf/Internal/FieldDescriptor.php
+++ b/php/src/Google/Protobuf/Internal/FieldDescriptor.php
@@ -46,8 +46,8 @@ class FieldDescriptor
     private $message_type;
     private $enum_type;
     private $packed;
-    private $is_map;
     private $oneof_index = -1;
+    private $proto3_optional;
 
     public function __construct()
     {
@@ -169,6 +169,16 @@ class FieldDescriptor
         return $this->packed;
     }
 
+    public function getProto3Optional()
+    {
+        return $this->proto3_optional;
+    }
+
+    public function setProto3Optional($proto3_optional)
+    {
+        $this->proto3_optional = $proto3_optional;
+    }
+
     public function isPackable()
     {
         return $this->isRepeated() && self::isTypePackable($this->type);
@@ -214,6 +224,10 @@ class FieldDescriptor
             $field_type !== GPBType::BYTES);
     }
 
+    /**
+     * @param FieldDescriptorProto $proto
+     * @return FieldDescriptor
+     */
     public static function getFieldDescriptor($proto)
     {
         $type_name = null;
@@ -269,6 +283,7 @@ class FieldDescriptor
         $field->setLabel($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 67b107f6a4..e685b26701 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()
@@ -64,6 +65,11 @@ class OneofDescriptor
         return $this->fields;
     }
 
+    public function isSynthetic()
+    {
+        return count($this->fields) === 1 && $this->fields[0]->getProto3Optional();
+    }
+
     public static function buildFromProto($oneof_proto, $desc, $index)
     {
         $oneof = new OneofDescriptor();
diff --git a/php/src/Google/Protobuf/OneofDescriptor.php b/php/src/Google/Protobuf/OneofDescriptor.php
index 92b4e279da..9717da8a77 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;
 
     /**
@@ -75,6 +76,6 @@ class OneofDescriptor
 
     public function isSynthetic()
     {
-      return $this->internal_desc->isSynthetic();
+        return $this->internal_desc->isSynthetic();
     }
 }