framework/i18n/Locale.php
public function init()
    {
        if (!extension_loaded('intl')) {
            throw new InvalidConfigException('Locale component requires PHP intl extension to be installed.');
        }

        if ($this->locale === null) {
            $this->locale = Yii::$app->language;
        }
    }
public function init()
    {
        if (!extension_loaded('intl')) {
            throw new InvalidConfigException('Locale component requires PHP intl extension to be installed.');
        }

        if ($this->locale === null) {
            $this->locale = Yii::$app->language;
        }
    }
{@inheritdoc}