framework/i18n/GettextMessageSource.php
protected function getMessageFilePath($language)
    {
        $messageFile = Yii::getAlias($this->basePath) . '/' . $language . '/' . $this->catalog;
        if ($this->useMoFile) {
            $messageFile .= self::MO_FILE_EXT;
        } else {
            $messageFile .= self::PO_FILE_EXT;
        }

        return $messageFile;
    }
protected function getMessageFilePath($language)
    {
        $messageFile = Yii::getAlias($this->basePath) . '/' . $language . '/' . $this->catalog;
        if ($this->useMoFile) {
            $messageFile .= self::MO_FILE_EXT;
        } else {
            $messageFile .= self::PO_FILE_EXT;
        }

        return $messageFile;
    }
Returns message file path for the specified language and category.

@param string $language the target language
@return string path to message file