PHP工作者不能并行工作

Question

I've got a problem: Worker threads seem to work serially. This is a very simple example just for a demonstration a problem.

I initialize my worker threads and run them. It should work in parallel however the result looks like it was processed serially.

PHP 5.6.12, Windows OS, Apache server

DBWorker: Which of course extends pThreads Worker class

class DBWorker extends Worker {

    private $str;

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

    public function run(){
        $i=0;
        while($i < 10) {
            echo "$this->str: $i
";
            $i++;
        }
    }
}

Initialization:

private $DBWorker1;
private $DBWorker2;
private $DBWorker3;

/* ... */

public function __construct(){
    $this->DBWorker1 = new DBWorker("worker1");
    $this->DBWorker2 = new DBWorker("worker2");
    $this->DBWorker3 = new DBWorker("worker3");
}

/* ... */

$this->DBWorker1->start();      
$this->DBWorker2->start();      
$this->DBWorker3->start();      


$i=0;
while($i < 10) {
    echo "parent: $i
";
    $i++;
}

var_dump($this->DBWorker1->shutdown());
var_dump($this->DBWorker2->shutdown());
var_dump($this->DBWorker3->shutdown());

Result:

parent: 0  
parent: 1  
parent: 2  
...  
parent: 6  
worker1: 0  
worker1: 1  
worker1: 2  
...  
worker1: 59  
worker2: 0  
worker2: 1  
worker2: 2  
...  
worker2: 59  
worker3: 0  
worker3: 1  
worker3: 2  
...  
worker3: 59  
parent: 7
parent: 8  
parent: 9  
bool(true)  
bool(true)  
bool(true)