关于laravel 数据库迁移中integer类型是无法指定长

Syntax error or aess violation: 1075 Incorrect table definition; there can be only one auto column and it must be defined as a key

int not null auto_increment primary key

 public function integer($column, $autoIncrement = false, $unsigned = false)
  {
  return $this->addColumn('integer', $column, pact('autoIncrement', 'unsigned'));
 }