framework/web/Response.php
public function redirect($url, $statusCode = 302, $checkAjax = true)
    {
        if (is_array($url) && isset($url[0])) {
            // ensure the route is absolute
            $url[0] = '/' . ltrim($url[0], '/');
        }
        $url = Url::to($url);
        if (strncmp($url, '/', 1) === 0 && strncmp($url, '//', 2) !== 0) {
            $url = Yii::$app->getRequest()->getHostInfo() . $url;
        }

        if ($checkAjax) {
            if (Yii::$app->getRequest()->getIsAjax()) {
                if (Yii::$app->getRequest()->getHeaders()->get('X-Ie-Redirect-Compatibility') !== null && $statusCode === 302) {
                    // Ajax 302 redirect in IE does not work. Change status code to 200. See https://github.com/yiisoft/yii2/issues/9670
                    $statusCode = 200;
                }
                if (Yii::$app->getRequest()->getIsPjax()) {
                    $this->getHeaders()->set('X-Pjax-Url', $url);
                } else {
                    $this->getHeaders()->set('X-Redirect', $url);
                }
            } else {
                $this->getHeaders()->set('Location', $url);
            }
        } else {
            $this->getHeaders()->set('Location', $url);
        }

        $this->setStatusCode($statusCode);

        return $this;
    }
public function redirect($url, $statusCode = 302, $checkAjax = true)
    {
        if (is_array($url) && isset($url[0])) {
            // ensure the route is absolute
            $url[0] = '/' . ltrim($url[0], '/');
        }
        $url = Url::to($url);
        if (strncmp($url, '/', 1) === 0 && strncmp($url, '//', 2) !== 0) {
            $url = Yii::$app->getRequest()->getHostInfo() . $url;
        }

        if ($checkAjax) {
            if (Yii::$app->getRequest()->getIsAjax()) {
                if (Yii::$app->getRequest()->getHeaders()->get('X-Ie-Redirect-Compatibility') !== null && $statusCode === 302) {
                    // Ajax 302 redirect in IE does not work. Change status code to 200. See https://github.com/yiisoft/yii2/issues/9670
                    $statusCode = 200;
                }
                if (Yii::$app->getRequest()->getIsPjax()) {
                    $this->getHeaders()->set('X-Pjax-Url', $url);
                } else {
                    $this->getHeaders()->set('X-Redirect', $url);
                }
            } else {
                $this->getHeaders()->set('Location', $url);
            }
        } else {
            $this->getHeaders()->set('Location', $url);
        }

        $this->setStatusCode($statusCode);

        return $this;
    }
Redirects the browser to the specified URL.

This method adds a "Location" header to the current response. Note that it does not send out
the header until [[send()]] is called. In a controller action you may use this method as follows:

```php
return Yii::$app->getResponse()->redirect($url);
```

In other places, if you want to send out the "Location" header immediately, you should use
the following code:

```php
Yii::$app->getResponse()->redirect($url)->send();
return;
```

In AJAX mode, this normally will not work as expected unless there are some
client-side JavaScript code handling the redirection. To help achieve this goal,
this method will send out a "X-Redirect" header instead of "Location".

If you use the "yii" JavaScript module, it will handle the AJAX redirection as
described above. Otherwise, you should write the following JavaScript code to
handle the redirection:

```javascript
$document.ajaxComplete(function (event, xhr, settings) {
var url = xhr && xhr.getResponseHeader('X-Redirect');
if (url) {
window.location = url;
}
});
```

@param string|array $url the URL to be redirected to. This can be in one of the following formats:

- a string representing a URL (e.g. "http://example.com")
- a string representing a URL alias (e.g. "@example.com")
- an array in the format of `[$route, ...name-value pairs...]` (e.g. `['site/index', 'ref' => 1]`).
Note that the route is with respect to the whole application, instead of relative to a controller or module.
[[Url::to()]] will be used to convert the array into a URL.

Any relative URL that starts with a single forward slash "/" will be converted
into an absolute one by prepending it with the host info of the current request.

@param int $statusCode the HTTP status code. Defaults to 302.
See <https://tools.ietf.org/html/rfc2616#section-10>
for details about HTTP status code
@param bool $checkAjax whether to specially handle AJAX (and PJAX) requests. Defaults to true,
meaning if the current request is an AJAX or PJAX request, then calling this method will cause the browser
to redirect to the given URL. If this is false, a `Location` header will be sent, which when received as
an AJAX/PJAX response, may NOT cause browser redirection.
Takes effect only when request header `X-Ie-Redirect-Compatibility` is absent.
@return $this the response object itself