如何配置Symfony1 PHP ORM以使用PostgreSQL SERIAL（自动增量）列

Question

Here i'm facing new issue on create auto increment id. I'm new to ORM Entity creation, here i struggle with create auto increment id using Entity relation its not working, every time insert record its stores empty value but i used query its working.

My Query :

 ALTER TABLE test ADD COLUMN autoincrement SERIAL; 

But i tried to create auto increment id using entity its not working, please help me if you can.

My ORM entity file :

autoincrement:
      type: integer
      column: autoincrement
      generator:
        strategy: AUTO

My PHP File :

/**
     * @var integer
     * @Column(type="integer")
     * @GeneratedValue
    */
    protected $autoincrement;