title: Override default property value in Doctrine2 Mapped Superclass
body: <p>The idea is that extending my <code>Employee</code> class and setting my <code>isManager</code> property would store it as true in the database whenever a DepartmentHead entity was created. This isn't working. Does anyone know why DepartmentHead entities are being stored with <code>isManager</code> equal to false?</p>
  
  <pre><code>/**
   * @Entity
   * @InheritanceType("JOINED")
   * @DiscriminatorColumn(name="discr", type="string")
   * @DiscriminatorMap({"employee" = "Employee", "dphead" = "DepartmentHead"})
   */
  class Employee
  {
      /**
       * @ORM\Id()
       * @ORM\GeneratedValue()
       * @ORM\Column(type="integer")
       */
      protected $id;
  
      /**
       * @ORM\Column(type="boolean")
       */
      protected static $isManager = false;
  
      /**
       * @return bool
       */
      public static function isManager(): bool
      {
          return static::$isManager;
      }
  
      /**
       * @param bool $isManager
       */
      public static function setIsManager(bool $isManager): void
      {
          static::$isManager = $isManager;
      }
  }
  
  /** 
   * @Entity()
   */
  class DepartmentHead extends Employee 
  {
      /**
       * @ORM\Id()
       * @ORM\GeneratedValue()
       * @ORM\Column(type="integer")
       */
      protected $id;
  
      protected static $isManager = true;
  }
  </code></pre>