PHP里的单例类写法实例

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：

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：

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：

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：

$instA = new SINGLEA();$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：

string"SINGLEA CHANGED: " (length=17)int110string"SINGLEB CHANGED: " (length=17)int-400