Yii框架实现的验证码、登录及退出功能示例

<?php
/**
 * UserIdentity represents the data needed to identity a user.
 * It contains the authentication method that checks if the provided
 * data can identity the user.
 */
class UserIdentity extends CUserIdentity
{
  /**
   * Authenticates a user.
   * The example implementation makes sure if the username and password
   * are both 'demo'.
   * In practical applications, this should be changed to authenticate
   * against some persistent user identity storage (e.g. database).
   * @return boolean whether authentication succeeds.
   */
  public function authenticate()
  {
    /*
    $users=array(
      // username => password
      'demo'=>'demo',
      'admin'=>'admin',
    );
    if(!isset($users[$this->username]))
      $this->errorCode=self::ERROR_USERNAME_INVALID;
    elseif($users[$this->username]!==$this->password)
      $this->errorCode=self::ERROR_PASSWORD_INVALID;
    else
      $this->errorCode=self::ERROR_NONE;
    return !$this->errorCode;
    */
    $user_model = Auth::model()->find('a_account=:name',array(':name'=>$this->username));
    if($user_model === null){
      $this -> errorCode = self::ERROR_USERNAME_INVALID;
      return false;
    } else if ($user_model->a_password !== md5($this -> password)){
      $this->errorCode=self::ERROR_PASSWORD_INVALID;
      return false;
    } else {
      $this->errorCode=self::ERROR_NONE;
      return true;
    }
  }
}