Update Document

README.md

@@ -22,6 +22,7 @@ Host in Beijing. Go to [demo](http://106.75.237.45:8080/).
 1. CURL
 1. PDO
 1. Mysqli
+1. Yar Client ([Yar](https://www.php.net/manual/en/book.yar.php), with `./configure --enable-yarclient=yes`)
 
 ## Contact Us
 * Submit an [issue](https://github.com/SkyAPM/SkyAPM-php-sdk/issues)

docs/zh/qa.md

@@ -19,6 +19,7 @@
  * php curl扩展发出的请求
  * php PDO扩展发出的请求
  * php mysqli扩展发出的请求
+ * php yar扩展(client)发出的请求: (需要在编译时指定：`./configure --enable-yarclient=yes`来启用)
 
 1. skywalking_get_trace_info()函数的返回值格式？
  * 返回值为数组。如果扩展加载但是未启用(`skywalking.enable=0`), 则返回空数组