update doc

README.md

 Sky Walking for php SDK| [中文](README.md)
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-# skywalking-php-sdk
-A manual PHP tracing SDK, compatible with skywalking APM
+**SkyWalking php SDK**: A client tool developed for PHP using SkyWalking APM tools. (It is a pity that it only supports writing log and checking curl currently.)
+SkyWalking APM : https://github.com/OpenSkywalking/skywalking
+
+* Automatic probe for PHP. **You don't need to modify the application code.**        
+  * It is a PHP extension developed by zendAPI.
+  * It can hook automatically for monnitoring nodes and collecting logs.
+  * It transfers with header informations automatically.
+* Manual probe.
+  * It is a php extension and contains some php classes. 
+  * It can compatible any versions of php.You can look over the codes in the class 'SkyWalking'.
+  * You need to add  business codes to monnitor.
+  
+# wiki document
+* [WIKI](https://github.com/OpenSkywalking/skywalking/wiki)
+
+
+# Using and installing
+*  php extensions(https://github.com/SkywalkingContrib/skywalking-php-sdk/tree/songzhian/sky-php7ext)
+*  php classes (https://github.com/SkywalkingContrib/skywalking-php-sdk/tree/songzhian/sdk-php)
+
+# Apply to
+*  version 1.0 applies to Skywalking 3.1 .
+
+# In the future.
+  * more php versions.
+  * more os.