Move JSONRPC_VERSION constant into RpcMessageInterface

Request::getParam() returns null if the parameter $name does not exist

Author: lucasnetau

src/Notification.php

@@ -7,10 +7,6 @@
  * @package EdgeTelemetrics\JSON_RPC
  */
 class Notification implements RpcMessageInterface {
-
-    /** @var string JSONRPC Version String */
-    const JSONRPC_VERSION = '2.0';
-
     /**
      * @var string A String containing the name of the method to be invoked
      */
@@ -73,7 +69,7 @@ public function setParam(string $name, $value)
      * Get all parameters
      * @return array
      */
-    public function getParams()
+    public function getParams() : array
     {
         return $this->params;
     }
@@ -85,7 +81,7 @@ public function getParams()
      */
     public function getParam(string $name)
     {
-        return $this->params[$name];
+        return $this->params[$name] ?? null;
     }
 
     /**

src/Response.php

@@ -133,7 +133,7 @@ public function isError(): bool
      */
     public function jsonSerialize() : array
     {
-        $record = ['jsonrpc' => Notification::JSONRPC_VERSION];
+        $record = ['jsonrpc' => self::JSONRPC_VERSION];
         $record['id'] = $this->id;
         if ($this->isError()) {
             $record['error'] = $this->result;

src/RpcMessageInterface.php

@@ -7,4 +7,7 @@
 /**
  * Interface for typehinting in functions that we want a JsonRpc object (request,notification,response)
  */
-interface RpcMessageInterface extends JsonSerializable {}
+interface RpcMessageInterface extends JsonSerializable {
+    /** @var string JSONRPC Version String */
+    const JSONRPC_VERSION = '2.0';
+}