empty() function return false with parameter of Thread empty array member

[2bright]

Environment

• PHP: 7.0.7
• pthreads: 3.1.6
• OS: ubuntu 14.04

Reproducing Code

<?php
class MyThread extends Thread {
    public function run(){
        $this->arr = (array)[];
        print_r("\$this->arr is " . (empty($this->arr) ? 'empty' : 'not empty') . "\n");
        $arr = (array)[];
        print_r("\$arr is " . (empty($arr) ? 'empty' : 'not empty') . "\n");
    }
}
$thread = new MyThread();
$thread->start();
?>

Expected Output

$this->arr is empty
$arr is empty

Actual Output

$this->arr is not empty
$arr is empty