Yii2 How to create a globally accessible variable that converts user's id to employee's id - yii2

Question

I have two tables that are related directly in a one-to-one relationship. One is the standard Yii2 user table (abbreviated field list here for clarity) and the other is the employee table that contains user_id. How can I create a globally accessible variable (and the actual code to access the employee id) that I can use anywhere in my application that will give me the logged in user's employee id and how would I call that variable? I wish I could say that I've tried a few things, but unfortunately I am relatively new to Yii2 and have no idea where to start with global variables like this. Thanks for any help.
user table:
id
username
password
etc
employee table:
id
user_id (related in a one-to-one relationship to the user table)
The Employee Model:
<?php
namespace frontend\models\base;
use Yii;
/**
* This is the base model class for table "employee".
*
* #property integer $id
* #property integer $user_id
*
* #property \common\models\User $user
*/
class Employee extends \yii\db\ActiveRecord
{
public function rules()
{
return [
[['user_id', 'required'],
[['user_id'], 'integer'],
[['user_id'], 'unique']
];
}
public static function tableName()
{
return 'employee';
}
public function attributeLabels()
{
return [
'id' => Yii::t('app', 'ID'),
'user_id' => Yii::t('app', 'User ID'),
];
}
/**
* #return \yii\db\ActiveQuery
*/
public function getUser()
{
return $this->hasOne(\common\models\User::className(), ['id' => 'user_id']);
}
}

Answer 1

A very simple way is the use of $param array
You can initially config the default value in
your_App\config\param.php
and accessing using
\Yii::$app->params['your_param_key']
Looking to your Employee model (for me ) you don't need a global var you could simply use the getUser
$myUser = Employee::user();
but you need the param you can assign using
\Yii::$app->params['my_user'] = Employee::user();
or in user
\Yii::$app->params['my_user'] = Yii::$app->user->id
or for retrive the model related to actual user from table
$myEmpModel = Employee::find()->where['user_id' => Yii::$app->user->id]->one();

Answer 2

I believe proper way is to use relations in your User model. First method is proper relation with activerecord, second one will get id using relation defined above it. so You will add these methods in your User model:
/**
* #return \yii\db\ActiveQuery
*/
public function getEmployee()
{
return $this->hasOne(Employee::className(), ['user_id' => 'id']);
}
public function getEmployeeId()
{
return $this->employee ? $this->employee->id : NULL; // set to NULL or anything you expect to be if record is not found
}
Then you can call it like this from everywhere in your app:
$employee_id = Yii::$app->user->identity->employeeid;
This will only work for User model because it implements Identity, otherwise you would need to instantiate model class first, lets say like this:
$user_id = 5; // 5 is id of user record in DB
$user = User::findOne($user_id);
$employee_id = $user->employeeid;
// or using first of 2 relations ...
$employee_id = $user->employee->id;