PHP pthreads：Thread :: start（）是否会返回FALSE？

I was wondering if there are circumstances where Thread::start() returns false. The manual isn't very clear about this.

I was able to let start() fail in the following cases. In all cases it throws a RuntimeException, so no false returned.

• Try to start a thread twice

  $thread = new Thread;
  $thread->start();
  $thread->start(); // RuntimeException
  

• Exhaust system resources

  class TestThread extends Thread
  {
      public function run()
      {
          sleep(PHP_INT_MAX);
      }
  }
  $threads = [];
  for (;;) {
      $thread = new TestThread;
      if (!$thread->start()) { // RuntimeException eventually
          echo 'FALSE returned.', PHP_EOL; // never printed
          break;
      }
      $threads[] = $thread;
  }
  

• Try to start thread again from thread (Note: You can start threads from threads; this is just an example to let it fail.)

  class TestThread extends Thread
  {
      public function run()
      {
          // necessary to see the exception
          set_exception_handler(function ($exception) {
              throw $exception;
          });
  
          self::start(); // RuntimeException
      }
  }
  (new TestThread)->start();