yii 2 Active Query中的数学运算

Question

Is there a way to subtract a value in a int column to say by 1?I have a button that when it is clicked it will call a function to save the data in the table but I want to know how to subtracting a number in a database using yii 2 I have tried the following code below but it had no effect. Can someone help me how to make math operations in yii 2?

public static function AddSubject($subjectid, $clientid){
    $subject = ActiveCurriculum::findOne(['subjectid' => $subjectid]);

    $activesubject = new ActiveSubject();
    $activesubject->clientid = $clientid;
    $activesubject->subjectid = $subject->subjectid;
    $activesubject->subjectcode = $subject->subjectcode;
    $activesubject->days = $subject->days;
    $activesubject->time = $subject->time;
    $activesubject->section = $subject->section;
    $activesubject->room = $subject->room;
    $activesubject->units = $subject->units;
    $subject->units = $subject->units - 1; //this should subtract the number 
    //of slots by 1 but now it is not working.
    $activesubject->save();

    return true;

    //return static::findOne(['subjectid' => $subjectid]);
                //->where(['subjectid' => $subjectid]);

  }

Answer 1

When You made some changes in your AR object and want your changes to be saved you should execute ->save():

$subject->units = $subject->units - 1; 
$subject->save();

Looks like You just forgot to do that.