ecshop实现用户名或Email都能登陆的修改方法

if ($this->check_user($username, $password) > 0)

if(is_email($username))
{
  $sql = "select ".$this->field_name." from ".$this->table($this->user_table)." where ".$this->field_email."='".$username."'";
  $username = $this->db->getOne($sql);
if(!$username) return false;
 }