小竹的部落格

:: 用來宣告使用於 static 的變數或方法

而

->是用於一般非 static 的變數與方法

範例參考自其他網站(感謝)

例如:

class DB
{
    private static $_instance = null;
     
    private static $_instanceCount = 0;
    private function __construct()
    {
        self::$_instanceCount ++;
    }
     
    public static function getInstance()
    {
        if (null === self::$_instance) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }
     
    public function getInstanceCount()
    {
        return self::$_instanceCount;
    }
}
$db1 = DB::getInstance();
echo $db1->getInstanceCount(), "\n"; // 1
$db2 = DB::getInstance();
echo $db2->getInstanceCount(), "\n"; // 1