PHP [OOP]:继承的内存分配

Question

请看下面的代码:

class A {
    public x = 5;
    public y = 6;
    public z = 7;
}

class B extends A {
    public m = 1;
    public n = 2;
}

$a = new A();
$b = new B()

从上面的代码中,$ a分配x内存,$ b分配y内存;

现在我的问题是从贝娄那是正确的？

x> y

x <y

Answer 1

这些是我的数字:

Starting allocation 62480
Allocated memory for new A() 328
Allocated memory for new B() 496

从而 x < y

这两个类定义是等价的

class B extends A {
    public $m = 1;
    public $n = 2;
}

class C {
    public $x = 5;
    public $y = 6;
    public $z = 7;
    public $m = 1;
    public $n = 2;
}

意思是你要将B的定义更改为C的定义,那么使用新的B()或新的C()的内存使用将完全相同.

要自己运行它,请使用此代码(作为示例)

$start = memory_get_usage();
echo "Starting allocation $start\n";
$a = new A();
$diff = memory_get_usage() - $start;
echo "Allocated memory for new A() $diff\n";
$b = new B();
$diff = memory_get_usage() - $start - $diff;
echo "Allocated memory for new B() $diff\n";