implement usr_msg_id

web/model.php

@@ -196,4 +196,22 @@ function api_return($http_code, $message)
 	http_response_code($http_code);
 	echo $message;
 	die();
+}
+
+/**
+ * @param String $str
+ * @param String[] $path
+ */
+function try_json($str, $path)
+{
+	try
+	{
+		$o = json_decode($str);
+		foreach ($path as $p) $o = $o[$p];
+		return $o;
+	}
+	catch (Exception $e)
+	{
+		return null;
+	}
 }