Url Helper
==========

Url 助手提供了一组静态方法来管理 URLs。


## Getting Common URLs <span id="getting-common-urls"></span>

这有两种方法你可以获得公共 URLs：home URL 和当前请求的 base URL 。按如下方法可以获得
home URL ：

```php
$relativeHomeUrl = Url::home();
$absoluteHomeUrl = Url::home(true);
$httpsAbsoluteHomeUrl = Url::home('https');
```

如果没有参数传递，生成的 URL 是相对路径。你即可以通过 `true` 获取当前 URL 的
schema 也可以指定用 (`https`, `http`) 中的哪个。

To get base URL of the current request use the following:
 
```php
$relativeBaseUrl = Url::base();
$absoluteBaseUrl = Url::base(true);
$httpsAbsoluteBaseUrl = Url::base('https');
```

The only parameter of the method works exactly the same as for `Url::home()`.


## Creating URLs <span id="creating-urls"></span>

In order to create URL to a given route use `Url::toRoute()` method. 此方法使用 [[\yii\web\UrlManager]] 来创建
一个 URL：

```php
$url = Url::toRoute(['product/view', 'id' => 42]);
```
 
You may specify the route as a string, e.g., `site/index`. You may also use an array if you want to specify additional
query parameters for the URL being created. 数组的格式必须按如下方式：

```php
// generates: /index.php?r=site/index&param1=value1&param2=value2
['site/index', 'param1' => 'value1', 'param2' => 'value2']
```

如果你想用锚创建一个 URL ，可以使用 `#` 作为数组的一个参数。例如，

```php
// generates: /index.php?r=site/index&param1=value1#name
['site/index', 'param1' => 'value1', '#' => 'name']
```

A route may be either absolute or relative. An absolute route has a leading slash (e.g. `/site/index`), while a relative
route has none (e.g. `site/index` or `index`). A relative route will be converted into an absolute one by the following rules:

- If the route is an empty string, the current [[\yii\web\Controller::route|route]] will be used;
- If the route contains no slashes at all (e.g. `index`), it is considered to be an action ID of the current controller
  and will be prepended with [[\yii\web\Controller::uniqueId]];
- If the route has no leading slash (e.g. `site/index`), it is considered to be a route relative to the current module
  and will be prepended with the module's [[\yii\base\Module::uniqueId|uniqueId]].
  
从版本 2.0.2 开始，you may specify a route in terms of an [alias](concept-aliases.md). 如果是这种情况，
the alias will first be converted into the actual route which will then be turned into an absolute route according
to the above rules.

下面是一些使用该方法的例子：

```php
// /index.php?r=site/index
echo Url::toRoute('site/index');

// /index.php?r=site/index&src=ref1#name
echo Url::toRoute(['site/index', 'src' => 'ref1', '#' => 'name']);

// /index.php?r=post/edit&id=100     assume the alias "@postEdit" is defined as "post/edit"
echo Url::toRoute(['@postEdit', 'id' => 100]);

// http://www.example.com/index.php?r=site/index
echo Url::toRoute('site/index', true);

// https://www.example.com/index.php?r=site/index
echo Url::toRoute('site/index', 'https');
```

有另一个方法 `Url::to()` 和 [[toRoute()]] 方法非常相似。The only difference is that this method
requires a route to be specified as an array only. 如果给出一个字符串，将被视为一个 URL。

第一个参数可能是：
         
- an array: [[toRoute()]] will be called to generate the URL. For example:
  `['site/index']`, `['post/index', 'page' => 2]`. Please refer to [[toRoute()]] for more details
  on how to specify a route.
- a string with a leading `@`: it is treated as an alias, and the corresponding aliased string
  will be returned.
- an empty string: the currently requested URL will be returned;
- a normal string: it will be returned as is.

When `$scheme` is specified (either a string or true), an absolute URL with host info (obtained from
[[\yii\web\UrlManager::hostInfo]]) will be returned. If `$url` is already an absolute URL, its scheme
will be replaced with the specified one.

下面是一些用法的示例：

```php
// /index.php?r=site/index
echo Url::to(['site/index']);

// /index.php?r=site/index&src=ref1#name
echo Url::to(['site/index', 'src' => 'ref1', '#' => 'name']);

// /index.php?r=post/edit&id=100     assume the alias "@postEdit" is defined as "post/edit"
echo Url::to(['@postEdit', 'id' => 100]);

// the currently requested URL
echo Url::to();

// /images/logo.gif
echo Url::to('@web/images/logo.gif');

// images/logo.gif
echo Url::to('images/logo.gif');

// http://www.example.com/images/logo.gif
echo Url::to('@web/images/logo.gif', true);

// https://www.example.com/images/logo.gif
echo Url::to('@web/images/logo.gif', 'https');
```

从版本 2.0.3 开始，you may use [[yii\helpers\Url::current()]] to create a URL based on the currently
requested route and GET parameters. You may modify or remove some of the GET parameters or add new ones by
passing a `$params` parameter to the method. 例如，

```php
// assume $_GET = ['id' => 123, 'src' => 'google'], current route is "post/view"

// /index.php?r=post/view&id=123&src=google
echo Url::current();

// /index.php?r=post/view&id=123
echo Url::current(['src' => null]);
// /index.php?r=post/view&id=100&src=google
echo Url::current(['id' => 100]);
```


## Remember URLs <span id="remember-urls"></span>

There are cases when you need to remember URL and afterwards use it during processing of the one of sequential requests.
它可以通过以下方式来实现：
 
```php
// Remember current URL 
Url::remember();

// Remember URL specified. See Url::to() for argument format.
Url::remember(['product/view', 'id' => 42]);

// Remember URL specified with a name given
Url::remember(['product/view', 'id' => 42], 'product');
```

In the next request we can get URL remembered in the following way:

```php
$url = Url::previous();
$productUrl = Url::previous('product');
```
                        
## 检查相对 URLs <span id="checking-relative-urls"></span>

To find out if URL is relative i.e. it doesn't have host info part, 你可以使用如下代码：
                             
```php
$isRelative = Url::isRelative('test/it');
```