Yii2: get value of attribute that has a behavior - php

Question

I'm using the TimestampBehaviour like this:
public function behaviors() {
return [
[
'class' => \yii\behaviors\TimestampBehavior::className(),
'createdAtAttribute' => 'usr_date_added',
'updatedAtAttribute' => 'usr_date_modified',
'value' => new \yii\db\Expression('UTC_TIMESTAMP()'),
],
];
}
Then if access it through the authenticated user like this...
Yii::$app->user->identity->usr_date_modified;
...I get the expression instead of the actual value:
object(yii\db\Expression)#38 (2) {
["expression"]=>
string(15) "UTC_TIMESTAMP()"
["params"]=>
array(0) {
}
}
If I do it like this I correctly get the actual value:
$user = app\models\User::findOne(51);
echo $user->usr_date_modified;
Why is that? And how can I get the actual value through the identity property?

Answer 1

The value while not saved in the database holds the information about how this actual value should be created - in your case it uses UTC_TIMESTAMP() MySQL function that will be called at the moment of saving this object into DB.
When you are retrieving object already saved in the database it takes whatever has been saved there (in your case the result of this MySQL function), so it gives you actual timestamp.
Before saving the object there is no point of checking this value.

Answer 2

I realized that I have modified an attribute and then called the save() method. You would think it should then hold the actual value after calling save() but it doesn't - I guess because doing the UPDATE query the database doesn't return the value. You need to call the refresh() method (see documentation) to make another SELECT query to get the new value. So you would need to do it like this:
Yii::$app->user->identity->usr_last_access = gmdate('Y-m-d H:i:s');
Yii::$app->user->identity->save();
Yii::$app->user->identity->refresh();