php 类的self关键字
self 表示当前类
//统计人数
class Student{
private static $num = 0; //静态变量在内存中就1份。
public function __construct()
{
self::$this->num++;
}
public function __destruct()
{
self::$this->num--;
}
public function show()
{
echo "总人数".self::$num;
}
}
$stu1 = new Student;
$stu2 = new Student;
$stu3 = new Student;
unset($stu2);
$stu3->show(); //总人数2下一篇：MySQL集合(set)数据类型