lib/CoreFilter/NativeCoreFilter.php
private function getLanguageFilter(array $languageCodes)
    {
        $languageFilters = array();

        foreach ($languageCodes as $languageCode) {
            // Include language
            $condition = new CustomField(self::FIELD_LANGUAGE, Operator::EQ, $languageCode);
            // Get list of excluded languages
            $excluded = $this->getExcludedLanguageCodes($languageCodes, $languageCode);

            // Combine if list is not empty
            if (!empty($excluded)) {
                $condition = new LogicalAnd(
                    array(
                        $condition,
                        new LogicalNot(
                            new CustomField(self::FIELD_LANGUAGES, Operator::IN, $excluded)
                        ),
                    )
                );
            }

            $languageFilters[] = $condition;
        }

        // Combine language fallback conditions with OR
        if (count($languageFilters) > 1) {
            $languageFilters = array(new LogicalOr($languageFilters));
        }

        // Exclude main languages index if used
        if ($this->hasMainLanguagesEndpoint) {
            $languageFilters[] = new LogicalNot(
                new CustomField(self::FIELD_IS_MAIN_LANGUAGES_INDEX, Operator::EQ, true)
            );
        }

        // Combine conditions
        if (count($languageFilters) > 1) {
            return new LogicalAnd($languageFilters);
        }

        return reset($languageFilters);
    }
private function getLanguageFilter(array $languageCodes)
    {
        $languageFilters = array();

        foreach ($languageCodes as $languageCode) {
            // Include language
            $condition = new CustomField(self::FIELD_LANGUAGE, Operator::EQ, $languageCode);
            // Get list of excluded languages
            $excluded = $this->getExcludedLanguageCodes($languageCodes, $languageCode);

            // Combine if list is not empty
            if (!empty($excluded)) {
                $condition = new LogicalAnd(
                    array(
                        $condition,
                        new LogicalNot(
                            new CustomField(self::FIELD_LANGUAGES, Operator::IN, $excluded)
                        ),
                    )
                );
            }

            $languageFilters[] = $condition;
        }

        // Combine language fallback conditions with OR
        if (count($languageFilters) > 1) {
            $languageFilters = array(new LogicalOr($languageFilters));
        }

        // Exclude main languages index if used
        if ($this->hasMainLanguagesEndpoint) {
            $languageFilters[] = new LogicalNot(
                new CustomField(self::FIELD_IS_MAIN_LANGUAGES_INDEX, Operator::EQ, true)
            );
        }

        // Combine conditions
        if (count($languageFilters) > 1) {
            return new LogicalAnd($languageFilters);
        }

        return reset($languageFilters);
    }
Returns criteria for prioritized languages fallback.

@param string[] $languageCodes

@return \eZ\Publish\API\Repository\Values\Content\Query\Criterion