yii2如何设置 keywords 和 descripition

在Yii2中如何设置title是非常容易的，只要在view.PHP里面设置$this->title="xxx"即可

代码如下：

$this->title="page title";

但是如何设置 keywords 和 descripition呢？

博主原本以为会有类似$this->keywords这种，然后果断发现没有。（强烈要求yii官方增加这个）

于是看了下源代码（View.php）发现有一个名为metaTags的变量 还有一个 registerMetaTag的方法

部分代码如下：

/** 
 * @var array the registered meta tags. 
 * @see registerMetaTag() 
 */ 
 public $metaTags; 
/** 
 * Registers a meta tag. 
 * @param array $options the HTML attributes for the meta tag. 
 * @param string $key the key that identifies the meta tag. If two meta tags are registered 
 * with the same key, the latter will overwrite the former. If this is null, the new meta tag 
 * will be appended to the existing ones. 
 */ 
 public function registerMetaTag($options, $key = null) 
 { 
     if ($key === null) { 
         $this->metaTags[] = Html::tag('meta', '', $options); 
     } else { 
         $this->metaTags[$key] = Html::tag('meta', '', $options); 
     } 
 }

registerMetaTag方法中用了Html::tag 这个方法

代码如下：

/** 
 * Generates a complete HTML tag. 
 * @param string $name the tag name 
 * @param string $content the content to be enclosed between the start and end tags. It will not be HTML-encoded. 
 * If this is coming from end users, you should consider [[encode()]] it to prevent XSS attacks. 
 * @param array $options the HTML tag attributes (HTML options) in terms of name-value pairs. 
 * These will be rendered as the attributes of the resulting tag. The values will be HTML-encoded using [[encode()]]. 
 * If a value is null, the corresponding attribute will not be rendered. 
 * 
 * For example when using `['class' => 'my-class', 'target' => '_blank', 'value' => null]` it will result in the 
 * html attributes rendered like this: `class="my-class" target="_blank"`. 
 * 
 * See [[renderTagAttributes()]] for details on how attributes are being rendered. 
 * 
 * @return string the generated HTML tag 
 * @see beginTag() 
 * @see endTag() 
 */ 
 public static function tag($name, $content = '', $options = []) 
 { 
 $html = "<$name" . static::renderTagAttributes($options) . '>'; 
 return isset(static::$voidElements[strtolower($name)]) ? $html : "$html$content</$name>"; 
 } 
在Html::tag中又使用了static::renderTagAttributes()方法
代码如下：
/** 
 * Renders the HTML tag attributes. 
 * 
 * Attributes whose values are of boolean type will be treated as 
 * [boolean attributes](http://www.w3.org/TR/html5/infrastructure.html#boolean-attributes). 
 * 
 * Attributes whose values are null will not be rendered. 
 * 
 * The values of attributes will be HTML-encoded using [[encode()]]. 
 * 
 * The "data" attribute is specially handled when it is receiving an array value. In this case, 
 * the array will be "expanded" and a list data attributes will be rendered. For example, 
 * if `'data' => ['id' => 1, 'name' => 'yii']`, then this will be rendered: 
 * `data-id="1" data-name="yii"`. 
 * Additionally `'data' => ['params' => ['id' => 1, 'name' => 'yii'], 'status' => 'ok']` will be rendered as: 
 * `data-params='{"id":1,"name":"yii"}' data-status="ok"`. 
 * 
 * @param array $attributes attributes to be rendered. The attribute values will be HTML-encoded using [[encode()]]. 
 * @return string the rendering result. If the attributes are not empty, they will be rendered 
 * into a string with a leading white space (so that it can be directly appended to the tag name 
 * in a tag. If there is no attribute, an empty string will be returned. 
 */ 
 public static function renderTagAttributes($attributes) 
 { 
     if (count($attributes) > 1) { 
         $sorted = []; 
         foreach (static::$attributeOrder as $name) { 
             if (isset($attributes[$name])) { 
                 $sorted[$name] = $attributes[$name]; 
              } 
         } 
     $attributes = array_merge($sorted, $attributes); 
     } 
     $html = ''; 
      foreach ($attributes as $name => $value) { 
         if (is_bool($value)) { 
             if ($value) { 
             $html .= " $name"; 
             } 
         } elseif (is_array($value) && $name === 'data') { 
             foreach ($value as $n => $v) { 
                 if (is_array($v)) { 
                     $html .= " $name-$n='" . Json::encode($v, JSON_HEX_APOS) . "'"; 
                 } else { 
                 $html .= " $name-$n=\"" . static::encode($v) . '"'; 
                 } 
             } 
         } elseif ($value !== null) { 
             $html .= " $name=\"" . static::encode($value) . '"'; 
         } 
     } 
 return $html; 
 }

从以上代码可以看出，如果我们在view.php中编写如下代码

$this->registerMetaTag(array("xxx"=>"xxx");//实际是$this->metaTags[]="<meta xxx"."='xxx'/>";然后再输出成<head>中

所以如果我们需要<meta name="keywords" contents="" />

那么有两种写法

$this->registerMetaTag(array("name"=>"keywords","content"=>"xxx"));//第一种 
$this->metaTags[]="<meta name='keywords' content='xxx'/>";//第二种