Class 'CActiveRecord' not found

when trying to create a model I get this error message Class ‘CActiveRecord’ not found pls why do i keep getting that error and what’s the possible solution

Post model code

class Jobseeker extends CActiveRecord


     public $password_repeat;

    public $new_password;

    public $holdPassword;

    public $month,$year,$day;

    public $Category;

    public $Provider;

    public $advertmeans;

    public $alertStatus;//whether alert has been sent for the day or not


     * Returns the static model of the specified AR class.

     * @param string $className active record class name.

     * @return Jobseekers the static model class


     protected function afterValidate()







                $this->password_repeat=  Companydetails::model()->encrypt($this->password_repeat);




         //   if(!empty($this->password_repeat))

          //  $this->password=Companydetails::model()->encrypt($this->password_repeat);



    public static function model($className=__CLASS__)


        return parent::model($className);



     * @return string the associated database table name


    public function tableName()


        return 'jobseekers';



     * @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('email, Address, City, State, Country, Phone, DOB, Sex,year,month,day', 'required','on'=>'demography'),


                    array('password, FirstName, LastName,email,City, State, Country,Phone', 'required','on'=>'skillfest'),

                     array('password, FirstName, LastName,email', 'required','on'=>'socialUser'), 

                        array('FirstName, LastName', 'required','on'=>'name'),

                        array("email, password, FirstName, LastName,password_repeat,DOB, Sex,year,month,day,City,Country,State",'required','on'=>'quickreg'),



            //array('password_repeat,email, password, FirstName, LastName, Address, City, State, Country, Phone, DOB, Sex,year,month,day', 'required','on'=>'newRegistration'),

            array('email, FirstName, LastName, City, State, Nationality, Country', 'length', 'max'=>100),

                    array('FirstName, LastName', 'length', 'max'=>15),

            array('password', 'length', 'max'=>300),

            array('Phone, MaritalStatus', 'length', 'max'=>20),

            array('Sex', 'length', 'max'=>10),



                        array('advertmeans','required','message'=>'Select how you heard about us.', 'on'=>'skillfest,demography,quickreg'),




                        array('DOB','date', 'format'=>array('yyyy-MM-dd','yyyy-MM-dd'), 'allowEmpty'=>false,'message'=>'The format of Date of birth is invalid. Example YYYY-MM-DD','on'=>'newRegistration,demography,quickreg'),

            // The following rule is used by search().

            // Please remove those attributes that should not be searched.



Has the model a namespace definition at top?

I would like to jump onto this.

I am very new to yii, installed it with the following composer call:

composer create-project --prefer-dist yiisoft/yii2-app-basic basic

But the directory /vendor/yiisoft/yii2/db/ar is missing.

The I tried to get it from github. Just to discover that CActiveRecord extends CModel, which I also don’t have.

I don’t understand why. I’am not shure, if I have to install an extension. If yes, then which one?

If I look to the API-Documentation it looks to me, as if CActiveRecord is part of the core.

I am a little bit confused. May someone explain to me, what’s wrong?