api/controllers/ApiRouter.php
public function outputSetFormat($sFormat)
    {
        if (static::isValidFormat($sFormat)) {
            $this->sOutputFormat = strtoupper($sFormat);
            return true;
        }

        return false;
    }
public function outputSetFormat($sFormat)
    {
        if (static::isValidFormat($sFormat)) {
            $this->sOutputFormat = strtoupper($sFormat);
            return true;
        }

        return false;
    }
Sets the output format

@param  string $sFormat The format to use

@return boolean