PHP里的单实例类在进行数据交换，节省内存上还是很有意义的。写个简单例子。
类1，单实例类本身：
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class UTIL { private static $instance; public function get() { if (!self::$instance) { self::$instance = new UTIL(); } return self::$instance; } public $number = 10; public function change($num) { $this->number += $num; } public function getNum() { return $this->number; }} |
类2，使用前述单实例类的应用类：
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class SINGLEA { private $numInst; function __construct() { $this->numInst = UTIL::get(); } public function change($num) { $this->numInst->change($num); } public function getNum() { return $this->numInst->getNum(); }} |
类3，同类2：
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class SINGLEB { private $numInst; function __construct() { $this->numInst = UTIL::get(); } public function change($num) { $this->numInst->change($num); } public function getNum() { return $this->numInst->getNum(); }} |
最后是调用的地方：
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$instA = new SINGLEA();$instA->change(100);var_dump('SINGLEA CHANGED: ');var_dump($instA->getNum());$instB = new SINGLEB();$instB->change(-510);var_dump('SINGLEB CHANGED: ');var_dump($instB->getNum()); |
最后的显示结果：
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string'SINGLEA CHANGED: ' (length=17)int110string'SINGLEB CHANGED: ' (length=17)int-400 |
