PHP pthread多线程

class test extends Thread {

    public $arg;
    public function __construct($arg){
        $this->arg = $arg;
    }

    public function run(){
        if($this->arg){
            sleep(1);
            echo "Hello " . $this->arg .‘：‘. date("Y-m-d H:i:s") . "<br>";
            sleep(1);
            // file_put_contents("./log.txt", date("Y-m-d H:i:s") . "I Am SonPthread" . "\r\n", FILE_APPEND);
        }
    }
}

$thread = new test("World");
echo "Start Pthread：" . date("Y-m-d H:i:s") . "<br>";
sleep(1);
$thread->start();
/*
* Hello World：2017-07-20 11:22:29
* Start Pthread：2017-07-20 11:22:27
* main thread：2017-07-20 11:22:28
*/

if($thread->start()){
    $thread->join();
}
/*
* Hello World：2017-07-20 11:23:23
* Start Pthread：2017-07-20 11:23:21
* main thread：2017-07-20 11:23:24
*/

echo "main thread：".date("Y-m-d H:i:s") . "<br>";;
file_put_contents("./main.txt", date("Y-m-d H:i:s") . "：Main Thread!" . "\r\n", FILE_APPEND);
echo "<br>";