對(duì)象串行化
Jun 08, 2016 pm 05:33 PM串行化可以把變量包括對(duì)象,轉(zhuǎn)化成連續(xù)bytes數(shù)據(jù). 你可以將串行化后的變量存在一個(gè)文件里或在網(wǎng)絡(luò)上傳輸. 然后再反串行化還原為原來(lái)的數(shù)據(jù). 你在反串行化類(lèi)的對(duì)象之前定義的類(lèi),PHP可以成功地存儲(chǔ)其對(duì)象的屬性和方法. 有時(shí)你可能需要一個(gè)對(duì)象在反串行化后立即執(zhí)行. 為了這樣的目的,PHP會(huì)自動(dòng)尋找__sleep和__wakeup方法.
當(dāng)一個(gè)對(duì)象被串行化,PHP會(huì)調(diào)用__sleep方法(假如存在的話(huà)). 在反串行化一個(gè)對(duì)象后,PHP 會(huì)調(diào)用__wakeup方法. 這兩個(gè)方法都不接受參數(shù). __sleep方法必須返回一個(gè)數(shù)組,包含需要串行化的屬性. PHP會(huì)拋棄其它屬性的值. 假如沒(méi)有__sleep方法,PHP將保存所有屬性.
例子6.16顯示了如何用__sleep和__wakeup方法來(lái)串行化一個(gè)對(duì)象. Id屬性是一個(gè)不打算保留在對(duì)象中的臨時(shí)屬性. __sleep方法保證在串行化的對(duì)象中不包含id屬性. 當(dāng)反串行化一個(gè)User對(duì)象,__wakeup方法建立id屬性的新值. 這個(gè)例子被設(shè)計(jì)成自我保持. 在實(shí)際開(kāi)發(fā)中,你可能發(fā)現(xiàn)包含資源(如圖像或數(shù)據(jù)流)的對(duì)象需要這些方法.
Listing 6.16 Object serialization
class User
{
public $name;
public $id;
function __construct()
{
//give user a unique ID 賦予一個(gè)不同的ID
$this->id = uniqid();
}
function __sleep()
{
//do not serialize this->id 不串行化id
return(array("name"));
}
function __wakeup()
{
//give user a unique ID
$this->id = uniqid();
}
}
//create object 建立一個(gè)對(duì)象
$u = new User;
$u->name = "Leon";
//serialize it 串行化 注重不串行化id屬性,id的值被拋棄
$s = serialize($u);
//unserialize it 反串行化 id被重新賦值
$u2 = unserialize($s);
//$u and $u2 have different IDs $u和$u2有不同的ID
print_r($u);
print_r($u2);
?>

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