在线等给分~PHP克癃问题！

PHP code:

<?php
class Corporate_Drone {
private $employeeid;
private $tiecolor;

function setEmployeeID($employeeid) {
$this->employeeid = $employeeid;
}

function getEmployeeID() {
return $this->employeeid;
}

function setTieColor($tiecolor) {
$this->tiecolor = $tiecolor;
}

function getTieColor() {
return $this->tiecolor;
}

function __clone(){
$this->tiecolor = "432423";
}
}

$drone1 = new Corporate_Drone();
$drone1->setEmployeeID("12345");
$drone1->setTieColor("3213123");
//克隆对象
$drone2 = clone $drone1;
$drone2->setEmployeeID("789");

printf("drone1 empoyeeID:%d<br/>", $drone1->getEmployeeID());
printf("drone1 tiecolor:%d<br/>", $drone1->getTieColor());

printf("drone2 empoyeeID:%d<br/>", $drone2->getEmployeeID());
printf("drone2 tiecolor:%d<br/>", $drone2->getTieColor());
?>


结果是这样：
drone1 empoyeeID:12345
drone1 tiecolor:3213123
drone2 empoyeeID:789
drone2 tiecolor:432423
$drone1->setEmployeeID("12345");为什么设置成字母就无法显示？？？

为什么drone1 tiecolor:3213123还会显示？？？？


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