Invalid Parameter Number. Parameter not defined - php

Question

UPDATE2:
I've created a new WebUser.php component in /protected/components as follows:
<?php
class WebUser extends CWebUser{
private $_model;
function getId(){
$user = $this->loadUser(Yii::app()->user->id);
return $user->id;
}
protected function loadUser($id=null){
if($this->_model===null)
{
if($id!==null)
{
$this->_model=Users::model()->findByPk($id);
}
return $this->_model;
}
}
}
I've registered the component in main.php as well. After uploading changes, my app still states that WebUser.getId is not defined.
UPDATE:
After making changes and then rolling them back, I'm getting a new error:
Property "CWebUser.getId" is not defined.
The snippet of code in question is:
$user = Users::model()->find('username=?', array(
Yii::app()->user->getId));
How and where should getId be set to reference the $id field in the Users model?
My UserController is throwing the following SQL Error:
CDbCommand failed to execute the SQL statement: SQLSTATE[HY093]: Invalid parameter number:
parameter was not defined. The SQL statement executed was: SELECT * FROM `users` `t` WHERE
username=? LIMIT 1
The error is being caused by this snippet of the controller:
public function actionProfile($id=''){
$user = Users::model()->find('username=?', array(Yii::app()->user->getId()));
if(!$id){
$id = $user->id;
if(!$id)
$this->redirect('login');
}
if( getUserSess('user_type') == 'Sitter') {
$this->render('profile_detail', array('user_id' => $id ));
} else {
$this->render('petowner_profile_detail',array(
'model'=>$this->loadModel($id),
));
}
}
The profile_detail view is as follows:
<?php
if(!$user_id){
$user_id = getUserSess('id');
}
$this->widget('ext.UserProfile.BasicProfile',array('user_id'=>$user_id)); ?>
<?php //$this->widget('ext.UserProfile.UserServices',array('user_id'=>$user_id)); ?>
The petowner_profile_detail view is as follows:
<?php $this->widget('zii.widgets.CDetailView', array(
'data'=>$model,
'attributes'=>array(
'username',
'email',
'phone',
'fname',
'lname',
'address1',
'address2',
'city',
'state',
'zip',
'is_year_old',
'user_type',
// 'register_date',
// 'varified_date',
// 'is_premium',
// 'last_login',
),
)); ?>
How do I rectify he SQL error?

Answer 1

UPDATE:
$user = Users::model()->find('username=:id', array(":id" => Yii::app()->user->id));
UPDATE2:
Yii::app()->user->getId() or Yii::app()->user->id not Yii::app()->user->getId