= 0) {
            if (($pos2 = strpos($this->pattern, '/', 2)) !== false) {
                $this->host = substr($this->pattern, 0, $pos2);
            } else {
                $this->host = $this->pattern;
            }
        } else {
            $this->pattern = '/' . $this->pattern . '/';
        }

        if (strpos($this->route, '<') !== false && preg_match_all('/<([\w._-]+)>/', $this->route, $matches)) {
            foreach ($matches[1] as $name) {
                $this->_routeParams[$name] = "<$name>";
            }
        }

        $this->translatePattern(true);
    }

    /**
     * Prepares [[$pattern]] on rule initialization - replace parameter names by placeholders.
     *
     * @param bool $allowAppendSlash Defines position of slash in the param pattern in [[$pattern]].
     * If `false` slash will be placed at the beginning of param pattern. If `true` slash position will be detected
     * depending on non-optional pattern part.
     */
    private function translatePattern($allowAppendSlash)
    {
        $tr = [
            '.' => '\\.',
            '*' => '\\*',
            '$' => '\\$',
            '[' => '\\[',
            ']' => '\\]',
            '(' => '\\(',
            ')' => '\\)',
        ];

        $tr2 = [];
        $requiredPatternPart = $this->pattern;
        $oldOffset = 0;
        if (preg_match_all('/<([\w._-]+):?([^>]+)?>/', $this->pattern, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER)) {
            $appendSlash = false;
            foreach ($matches as $match) {
                $name = $match[1][0];
                $pattern = isset($match[2][0]) ? $match[2][0] : '[^\/]+';
                $placeholder = 'a' . hash('crc32b', $name); // placeholder must begin with a letter
                $this->placeholders[$placeholder] = $name;
                if (array_key_exists($name, $this->defaults)) {
                    $length = strlen($match[0][0]);
                    $offset = $match[0][1];
                    $requiredPatternPart = str_replace("/{$match[0][0]}/", '//', $requiredPatternPart);
                    if (
                        $allowAppendSlash
                        && ($appendSlash || $offset === 1)
                        && (($offset - $oldOffset) === 1)
                        && isset($this->pattern[$offset + $length])
                        && $this->pattern[$offset + $length] === '/'
                        && isset($this->pattern[$offset + $length + 1])
                    ) {
                        // if pattern starts from optional params, put slash at the end of param pattern
                        // @see https://github.com/yiisoft/yii2/issues/13086
                        $appendSlash = true;
                        $tr["<$name>/"] = "((?P<$placeholder>$pattern)/)?";
                    } elseif (
                        $offset > 1
                        && $this->pattern[$offset - 1] === '/'
                        && (!isset($this->pattern[$offset + $length]) || $this->pattern[$offset + $length] === '/')
                    ) {
                        $appendSlash = false;
                        $tr["/<$name>"] = "(/(?P<$placeholder>$pattern))?";
                    }
                    $tr["<$name>"] = "(?P<$placeholder>$pattern)?";
                    $oldOffset = $offset + $length;
                } else {
                    $appendSlash = false;
                    $tr["<$name>"] = "(?P<$placeholder>$pattern)";
                }

                if (isset($this->_routeParams[$name])) {
                    $tr2["<$name>"] = "(?P<$placeholder>$pattern)";
                } else {
                    $this->_paramRules[$name] = $pattern === '[^\/]+' ? '' : "#^$pattern$#u";
                }
            }
        }

        // we have only optional params in route - ensure slash position on param patterns
        if ($allowAppendSlash && trim($requiredPatternPart, '/') === '') {
            $this->translatePattern(false);
            return;
        }

        $this->_template = preg_replace('/<([\w._-]+):?([^>]+)?>/', '<$1>', $this->pattern);
        $this->pattern = '#^' . trim(strtr($this->_template, $tr), '/') . '$#u';

        // if host starts with relative scheme, then insert pattern to match any
        if (strncmp($this->host, '//', 2) === 0) {
            $this->pattern = substr_replace($this->pattern, '[\w]+://', 2, 0);
        }

        if (!empty($this->_routeParams)) {
            $this->_routeRule = '#^' . strtr($this->route, $tr2) . '$#u';
        }
    }

    /**
     * @param UrlManager $manager the URL manager
     * @return UrlNormalizer|null
     * @since 2.0.10
     */
    protected function getNormalizer($manager)
    {
        if ($this->normalizer === null) {
            return $manager->normalizer;
        }

        return $this->normalizer;
    }

    /**
     * @param UrlManager $manager the URL manager
     * @return bool
     * @since 2.0.10
     */
    protected function hasNormalizer($manager)
    {
        return $this->getNormalizer($manager) instanceof UrlNormalizer;
    }

    /**
     * Parses the given request and returns the corresponding route and parameters.
     * @param UrlManager $manager the URL manager
     * @param Request $request the request component
     * @return array|bool the parsing result. The route and the parameters are returned as an array.
     * If `false`, it means this rule cannot be used to parse this path info.
     */
    public function parseRequest($manager, $request)
    {
        if ($this->mode === self::CREATION_ONLY) {
            return false;
        }

        if (!empty($this->verb) && !in_array($request->getMethod(), $this->verb, true)) {
            return false;
        }

        $suffix = (string) ($this->suffix === null ? $manager->suffix : $this->suffix);
        $pathInfo = $request->getPathInfo();
        $normalized = false;
        if ($this->hasNormalizer($manager)) {
            $pathInfo = $this->getNormalizer($manager)->normalizePathInfo($pathInfo, $suffix, $normalized);
        }
        if ($suffix !== '' && $pathInfo !== '') {
            $n = strlen($suffix);
            if (substr_compare($pathInfo, $suffix, -$n, $n) === 0) {
                $pathInfo = substr($pathInfo, 0, -$n);
                if ($pathInfo === '') {
                    // suffix alone is not allowed
                    return false;
                }
            } else {
                return false;
            }
        }

        if ($this->host !== null) {
            $pathInfo = strtolower($request->getHostInfo()) . ($pathInfo === '' ? '' : '/' . $pathInfo);
        }

        if (!preg_match($this->pattern, $pathInfo, $matches)) {
            return false;
        }
        $matches = $this->substitutePlaceholderNames($matches);

        foreach ($this->defaults as $name => $value) {
            if (!isset($matches[$name]) || $matches[$name] === '') {
                $matches[$name] = $value;
            }
        }
        $params = $this->defaults;
        $tr = [];
        foreach ($matches as $name => $value) {
            if (isset($this->_routeParams[$name])) {
                $tr[$this->_routeParams[$name]] = $value;
                unset($params[$name]);
            } elseif (isset($this->_paramRules[$name])) {
                $params[$name] = $value;
            }
        }
        if ($this->_routeRule !== null) {
            $route = strtr($this->route, $tr);
        } else {
            $route = $this->route;
        }

        Yii::debug("Request parsed with URL rule: {$this->name}", __METHOD__);

        if ($normalized) {
            // pathInfo was changed by normalizer - we need also normalize route
            return $this->getNormalizer($manager)->normalizeRoute([$route, $params]);
        }

        return [$route, $params];
    }

    /**
     * Creates a URL according to the given route and parameters.
     * @param UrlManager $manager the URL manager
     * @param string $route the route. It should not have slashes at the beginning or the end.
     * @param array $params the parameters
     * @return string|bool the created URL, or `false` if this rule cannot be used for creating this URL.
     */
    public function createUrl($manager, $route, $params)
    {
        if ($this->mode === self::PARSING_ONLY) {
            $this->createStatus = self::CREATE_STATUS_PARSING_ONLY;
            return false;
        }

        $tr = [];

        // match the route part first
        if ($route !== $this->route) {
            if ($this->_routeRule !== null && preg_match($this->_routeRule, $route, $matches)) {
                $matches = $this->substitutePlaceholderNames($matches);
                foreach ($this->_routeParams as $name => $token) {
                    if (isset($this->defaults[$name]) && strcmp($this->defaults[$name], $matches[$name]) === 0) {
                        $tr[$token] = '';
                    } else {
                        $tr[$token] = $matches[$name];
                    }
                }
            } else {
                $this->createStatus = self::CREATE_STATUS_ROUTE_MISMATCH;
                return false;
            }
        }

        // match default params
        // if a default param is not in the route pattern, its value must also be matched
        foreach ($this->defaults as $name => $value) {
            if (isset($this->_routeParams[$name])) {
                continue;
            }
            if (!isset($params[$name])) {
                // allow omit empty optional params
                // @see https://github.com/yiisoft/yii2/issues/10970
                if (in_array($name, $this->placeholders) && strcmp($value, '') === 0) {
                    $params[$name] = '';
                } else {
                    $this->createStatus = self::CREATE_STATUS_PARAMS_MISMATCH;
                    return false;
                }
            }
            if (strcmp($params[$name], $value) === 0) { // strcmp will do string conversion automatically
                unset($params[$name]);
                if (isset($this->_paramRules[$name])) {
                    $tr["<$name>"] = '';
                }
            } elseif (!isset($this->_paramRules[$name])) {
                $this->createStatus = self::CREATE_STATUS_PARAMS_MISMATCH;
                return false;
            }
        }

        // match params in the pattern
        foreach ($this->_paramRules as $name => $rule) {
            if (isset($params[$name]) && !is_array($params[$name]) && ($rule === '' || preg_match($rule, $params[$name]))) {
                $tr["<$name>"] = $this->encodeParams ? urlencode($params[$name]) : $params[$name];
                unset($params[$name]);
            } elseif (!isset($this->defaults[$name]) || isset($params[$name])) {
                $this->createStatus = self::CREATE_STATUS_PARAMS_MISMATCH;
                return false;
            }
        }

        $url = $this->trimSlashes(strtr($this->_template, $tr));
        if ($this->host !== null) {
            $pos = strpos($url, '/', 8);
            if ($pos !== false) {
                $url = substr($url, 0, $pos) . preg_replace('#/+#', '/', substr($url, $pos));
            }
        } elseif (strpos($url, '//') !== false) {
            $url = preg_replace('#/+#', '/', trim($url, '/'));
        }

        if ($url !== '') {
            $url .= ($this->suffix === null ? $manager->suffix : $this->suffix);
        }

        if (!empty($params) && ($query = http_build_query($params)) !== '') {
            $url .= '?' . $query;
        }

        $this->createStatus = self::CREATE_STATUS_SUCCESS;
        return $url;
    }

    /**
     * Returns status of the URL creation after the last [[createUrl()]] call.
     *
     * @return null|int Status of the URL creation after the last [[createUrl()]] call. `null` if rule does not provide
     * info about create status.
     * @see $createStatus
     * @since 2.0.12
     */
    public function getCreateUrlStatus()
    {
        return $this->createStatus;
    }

    /**
     * Returns list of regex for matching parameter.
     * @return array parameter keys and regexp rules.
     *
     * @since 2.0.6
     */
    protected function getParamRules()
    {
        return $this->_paramRules;
    }

    /**
     * Iterates over [[placeholders]] and checks whether each placeholder exists as a key in $matches array.
     * When found - replaces this placeholder key with a appropriate name of matching parameter.
     * Used in [[parseRequest()]], [[createUrl()]].
     *
     * @param array $matches result of `preg_match()` call
     * @return array input array with replaced placeholder keys
     * @see placeholders
     * @since 2.0.7
     */
    protected function substitutePlaceholderNames(array $matches)
    {
        foreach ($this->placeholders as $placeholder => $name) {
            if (isset($matches[$placeholder])) {
                $matches[$name] = $matches[$placeholder];
                unset($matches[$placeholder]);
            }
        }

        return $matches;
    }

    /**
     * Trim slashes in passed string. If string begins with '//', two slashes are left as is
     * in the beginning of a string.
     *
     * @param string $string
     * @return string
     */
    private function trimSlashes($string)
    {
        if (strncmp($string, '//', 2) === 0) {
            return '//' . trim($string, '/');
        }

        return trim($string, '/');
    }
}
<pre>An Error occurred while handling another error:
yii\web\HeadersAlreadySentException: Headers already sent in /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/UrlRule.php on line 1. in /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/Response.php:373
Stack trace:
#0 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/Response.php(346): yii\web\Response-&gt;sendHeaders()
#1 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/ErrorHandler.php(136): yii\web\Response-&gt;send()
#2 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/ErrorHandler.php(135): yii\web\ErrorHandler-&gt;renderException()
#3 [internal function]: yii\base\ErrorHandler-&gt;handleException()
#4 {main}
Previous exception:
yii\base\UnknownClassException: Unable to find &#039;yii\web\UrlRule&#039; in file: /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/UrlRule.php. Namespace missing? in /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/BaseYii.php:296
Stack trace:
#0 [internal function]: yii\BaseYii::autoload()
#1 [internal function]: spl_autoload_call()
#2 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/caching/Cache.php(138): unserialize()
#3 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/UrlManager.php(299): yii\caching\Cache-&gt;get()
#4 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/UrlManager.php(236): yii\web\UrlManager-&gt;getBuiltRulesFromCache()
#5 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/UrlManager.php(198): yii\web\UrlManager-&gt;buildRules()
#6 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/BaseObject.php(109): yii\web\UrlManager-&gt;init()
#7 [internal function]: yii\base\BaseObject-&gt;__construct()
#8 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/di/Container.php(420): ReflectionClass-&gt;newInstanceArgs()
#9 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/di/Container.php(171): yii\di\Container-&gt;build()
#10 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/BaseYii.php(365): yii\di\Container-&gt;get()
#11 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/di/ServiceLocator.php(137): yii\BaseYii::createObject()
#12 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/Module.php(748): yii\di\ServiceLocator-&gt;get()
#13 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/Application.php(577): yii\base\Module-&gt;get()
#14 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2-gii/src/Module.php(89): yii\base\Application-&gt;getUrlManager()
#15 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/Application.php(333): yii\gii\Module-&gt;bootstrap()
#16 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/web/Application.php(70): yii\base\Application-&gt;bootstrap()
#17 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/Application.php(279): yii\web\Application-&gt;bootstrap()
#18 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/BaseObject.php(109): yii\base\Application-&gt;init()
#19 /var/www/vhosts/vassh.com.vn/vassh.vn/vendor/yiisoft/yii2/base/Application.php(212): yii\base\BaseObject-&gt;__construct()
#20 /var/www/vhosts/vassh.com.vn/vassh.vn/index.php(17): yii\base\Application-&gt;__construct()
#21 {main}</pre>