documentation updates

Signed-off-by: Demin Yin <deminy@deminy.net>

src/swoole/Swoole/Process.php

@@ -22,8 +22,22 @@ class Process
 
     public $msgQueueKey;
 
+    /**
+     * Process ID. This is to uniquely identify the process in the OS.
+     *
+     * @var int
+     */
     public $pid;
 
+    /**
+     * ID of the process.
+     *
+     * In a Swoole program (e.g., a Swoole-based server), there are different types of processes, including event worker
+     * processes, task worker processes, and user worker processes. This ID is to uniquely identify the process in the
+     * running Swoole program.
+     *
+     * @var int
+     */
     public $id;
 
     private $callback;

src/swoole/Swoole/Server.php

@@ -467,9 +467,11 @@ public function connection_list($start_fd, $find_count = null)
     public function sendMessage($message, $dst_worker_id)
     {
     }
+
     /**
      * @param \Swoole\Process $process
-     * @return int
+     * @return int|false Return the ID of the process (\Swoole\Process::$id) back if succeeds; otherwise return FALSE.
+     * @see \Swoole\Process::$id
      */
     public function addProcess(Process $process)
     {