framework/i18n/I18N.php
public function format($message, $params, $language)
    {
        $params = (array) $params;
        if ($params === []) {
            return $message;
        }

        if (preg_match('~{\s*[\w.]+\s*,~u', $message)) {
            $formatter = $this->getMessageFormatter();
            $result = $formatter->format($message, $params, $language);
            if ($result === false) {
                $errorMessage = $formatter->getErrorMessage();
                Yii::warning("Formatting message for language '$language' failed with error: $errorMessage. The message being formatted was: $message.", __METHOD__);

                return $message;
            }

            return $result;
        }

        $p = [];
        foreach ($params as $name => $value) {
            $p['{' . $name . '}'] = $value;
        }

        return strtr($message, $p);
    }
public function format($message, $params, $language)
    {
        $params = (array) $params;
        if ($params === []) {
            return $message;
        }

        if (preg_match('~{\s*[\w.]+\s*,~u', $message)) {
            $formatter = $this->getMessageFormatter();
            $result = $formatter->format($message, $params, $language);
            if ($result === false) {
                $errorMessage = $formatter->getErrorMessage();
                Yii::warning("Formatting message for language '$language' failed with error: $errorMessage. The message being formatted was: $message.", __METHOD__);

                return $message;
            }

            return $result;
        }

        $p = [];
        foreach ($params as $name => $value) {
            $p['{' . $name . '}'] = $value;
        }

        return strtr($message, $p);
    }
Formats a message using [[MessageFormatter]].

@param string $message the message to be formatted.
@param array $params the parameters that will be used to replace the corresponding placeholders in the message.
@param string $language the language code (e.g. `en-US`, `en`).
@return string the formatted message.