eZ\Publish\Core\Repository\Values\Content\Content::getField PHP Method

    public function getField($fieldDefIdentifier, $languageCode = null)
    {
        if (null === $languageCode) {
            $languageCode = $this->versionInfo->contentInfo->mainLanguageCode;
        }
        foreach ($this->getFields() as $field) {
            if ($field->fieldDefIdentifier === $fieldDefIdentifier && $field->languageCode === $languageCode) {
                return $field;
            }
        }
        return null;
    }