Ohh hmm, you’re right it isn’t defined in my model\Post.php class. I will copy/paste it here and investigation too.
<?php
/**
* This is the model class for table "{{post}}".
*
* The followings are the available columns in table '{{post}}':
* @property integer $id
* @property string $title
* @property string $content
* @property string $tags
* @property integer $status
* @property integer $create_time
* @property integer $update_time
* @property integer $author_id
*
* The followings are the available model relations:
* @property Comment[] $comments
* @property User $author
*/
class Post extends CActiveRecord
{
const STATUS_DRAFT = 1;
const STATUS_PUBLISHED = 2;
const STATUS_ARCHIVED = 3;
private $_oldTags;
protected function beforeSave() {
if (parent::beforeSave()) {
if ($this->isNewRecord) {
$this->create_time = $this->update_time = time();
$this->author_id = Yii::app()->user->id;
} else
$this->update_time = time();
return true;
} else
return false;
}
protected function afterSave() {
parent::afterSave();
Tag::model()->updateFrequency($this->_oldTags, $this->tags);
}
protected function afterFind() {
parent::afterFind();
$this->_oldTags = $this->tags;
}
/**
* Returns the static model of the specified AR class.
* @param string $className active record class name.
* @return Post the static model class
*/
public static function model($className=__CLASS__)
{
return parent::model($className);
}
/**
* @return string the associated database table name
*/
public function tableName()
{
return '{{post}}';
}
public function rules() {
return array (
array ('title, content, status', 'required'),
array ('title', 'length', 'max' => 128),
array ('status', 'in', 'range' => array(1,2,3)),
array ('tags', 'match', 'pattern' => '/^[\w\s,]+$/',
'message' => 'Tags can only contain word characters.'),
array ('tags', 'noramlizeTags'),
array('title, status', 'safe', 'on' => 'search'),
);
}
/** Generated rules()
*
* @return array validation rules for model attributes.
*
public function rules()
{
// NOTE: you should only define rules for those attributes that
// will receive user inputs.
return array(
array('title, content, status, author_id', 'required'),
array('status, create_time, update_time, author_id', 'numerical', 'integerOnly'=>true),
array('title', 'length', 'max'=>128),
array('tags', 'safe'),
// The following rule is used by search().
// Please remove those attributes that should not be searched.
array('id, title, content, tags, status, create_time, update_time, author_id', 'safe', 'on'=>'search'),
);
}
*/
/**
* @return array relational rules.
*/
public function relations()
{
// NOTE: you may need to adjust the relation name and the related
// class name for the relations automatically generated below.
return array(
'comments' => array(self::HAS_MANY, 'Comment', 'post_id'),
'author' => array(self::BELONGS_TO, 'User', 'author_id'),
);
}
/**
* @return array customized attribute labels (name=>label)
*/
public function attributeLabels()
{
return array(
'id' => 'ID',
'title' => 'Title',
'content' => 'Content',
'tags' => 'Tags',
'status' => 'Status',
'create_time' => 'Create Time',
'update_time' => 'Update Time',
'author_id' => 'Author',
);
}
/**
* Retrieves a list of models based on the current search/filter conditions.
* @return CActiveDataProvider the data provider that can return the models based on the search/filter conditions.
*/
public function search()
{
// Warning: Please modify the following code to remove attributes that
// should not be searched.
$criteria=new CDbCriteria;
$criteria->compare('id',$this->id);
$criteria->compare('title',$this->title,true);
$criteria->compare('content',$this->content,true);
$criteria->compare('tags',$this->tags,true);
$criteria->compare('status',$this->status);
$criteria->compare('create_time',$this->create_time);
$criteria->compare('update_time',$this->update_time);
$criteria->compare('author_id',$this->author_id);
return new CActiveDataProvider($this, array(
'criteria'=>$criteria,
));
}
public function normalizeTags($attribute, $params) {
$this->tags = Tag::array2string(array_unique(Tag::string2array($this->tags)));
}
public function getUrl() {
return Yii::app()->createUrl('post/view', array(
'id' => $this-id,
'title' => $this->title,
));
}
}
Edit:
Uh-Oh! Totally newbie mistake! I put the relations function in the wrong model. 
See here: http://www.yiiframework.com/doc/blog/1.1/en/post.model#customizing-x-16x-method
It works now!