Update readme

Author: jmjoy

README.md

@@ -4,11 +4,15 @@
 
 [The Jieba Chinese Word Segmentation](https://github.com/messense/jieba-rs) Implemented in Rust Bound for PHP.
 
+## Requirements
+
+- rust
+- php-dev
+
 ## Build
 
 ```shell
-# Optional, specify if php isn't installed globally,
-# this environment is used by `phper-sys`.
+# Optional, specify if php isn't installed globally.
 #
 # export PHP_CONFIG=<Your path of php-config>
 
@@ -19,9 +23,25 @@ cargo build --release
 ## Run
 
 ```shell
+php -d "extension=target/debug/libjieba.so" --ri jieba
+
 php -d "extension=target/debug/libjieba.so" -r "print_r((new Jieba())->cut('我们中出了一个叛徒'));"
 ```
 
+## API
+
+```php
+class Jieba {
+    public function __construct();
+
+    public function cut(string $sentence, bool $hmm): array;
+
+    public function cutForSearch(string $sentence, bool $hmm): array;
+
+    public function cutAll(string $sentence): array;
+}
+```
+
 ## Examples
 
 ```php