src/Helpers/Html.php
public static function encode($content, $doubleEncode = true, $encoding = null)
    {
        if (!isset($encoding)) {
            $encoding = Reaction::$app ? Reaction::$app->charset : 'UTF-8';
        }
        return htmlspecialchars($content, ENT_QUOTES | ENT_SUBSTITUTE, $encoding, $doubleEncode);
    }
public static function encode($content, $doubleEncode = true, $encoding = null)
    {
        if (!isset($encoding)) {
            $encoding = Reaction::$app ? Reaction::$app->charset : 'UTF-8';
        }
        return htmlspecialchars($content, ENT_QUOTES | ENT_SUBSTITUTE, $encoding, $doubleEncode);
    }
Encodes special characters into HTML entities.
The [[\yii\base\Application::charset|application charset]] will be used for encoding.
@param string $content the content to be encoded
@param bool   $doubleEncode whether to encode HTML entities in `$content`. If false,
HTML entities in `$content` will not be further encoded.
@param string $encoding
@return string the encoded content
@see decode()
@see http://www.php.net/manual/en/function.htmlspecialchars.php