Yii2 Timestamp Behavior

<?php

namespace common\components;

use \yii\base\Behavior;
use \yii\base\ModelEvent;
use \yii\db\ActiveRecord;
use \yii\db\Expression;

/**
 *
 */
class TimestampBehavior extends Behavior
{
    /**
     * @var string
     */
    public $createAttribute = 'created_at';

    /**
     * @var string
     */
    public $updateAttribute = 'updated_at';

    /**
     * @var boolean
     */
    public $setUpdateOnCreate = true;

    /**
     * @var string
     */
    public $timestampExpression;

    /**
     * @var array
     */
    public static $typeMap = array(
        'datetime' => 'NOW()',
        'timestamp' => 'NOW()',
        'date' => 'NOW()',
    );

    public function events()
    {
        return array(
            ActiveRecord::EVENT_BEFORE_INSERT => 'onInsert',
            ActiveRecord::EVENT_BEFORE_UPDATE => 'onUpdate',
        );
    }

    /**
     * @param ModelEvent $event
     */
    public function onInsert($event)
    {
        if ($this->createAttribute !== null) {
            $this->owner->{$this->createAttribute} = $this->getTimestampByAttribute($this->createAttribute);
        }
        if ($this->updateAttribute !== null && $this->setUpdateOnCreate) {
            $this->owner->{$this->updateAttribute} = $this->getTimestampByAttribute($this->updateAttribute);
        }
    }

    /**
     * @param ModelEvent $event
     */
    public function onUpdate($event)
    {
        if ($this->updateAttribute !== null) {
            $this->owner->{$this->updateAttribute} = $this->getTimestampByAttribute($this->updateAttribute);
        }
    }

    /**
     * @param string $attribute
     * @return integer|Expression
     */
    protected function getTimestampByAttribute($attribute)
    {
        if ($this->timestampExpression instanceof Expression) {
            return $this->timestampExpression;
        } elseif ($this->timestampExpression !== null) {
            return eval('return ' . $this->timestampExpression . ';');
        }

        $type = $this->owner->getTableSchema()->getColumn($attribute)->type;
        return $this->getTimestampByType($type);
    }

    /**
     * @param string $type
     * @return integer|Expression
     */
    protected function getTimestampByType($type)
    {
        if (isset(static::$typeMap[$type])) {
            return new Expression(static::$typeMap[$type]);
        } else {
            return time();
        }
    }
}