yiisoft / yii2

framework/db/ExpressionBuilder.php

<?php
/**
 * @link https://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license https://www.yiiframework.com/license/
 */

namespace yii\db;

/**
 * Class ExpressionBuilder builds objects of [[yii\db\Expression]] class.
 *
 * @author Dmitry Naumenko <d.naumenko.a@gmail.com>
 * @since 2.0.14
 */
class ExpressionBuilder implements ExpressionBuilderInterface
{
    use ExpressionBuilderTrait;


    /**
     * {@inheritdoc}
     * @param Expression|ExpressionInterface $expression the expression to be built
     */
    public function build(ExpressionInterface $expression, array &$params = [])
    {
        $params = array_merge($params, $expression->params);

Accessing params on the interface yii\db\ExpressionInterface suggest that you code against a concrete implementation. How about adding an instanceof check?

        return $expression->__toString();

The method __toString() does not exist on yii\db\ExpressionInterface. It seems like you code against a sub-type of yii\db\ExpressionInterface such as yii\db\Query or yii\db\Expression.

    }
}