在PHP中，是否可以在非静态类中使用函数，但也不是实例函数？

Question

In PHP, is it possible to have a function within a class that's non-static, but also isn't an instance function?

For example, if I have the following:

class A
{
   public $i;

   function setValue($val) {
      $this->i = $val;
   }
}  

$a1 = new A;
$a1->setValue(5);
echo $a1->i; // result: 5

$a2 = new A;
$a2->setValue(2);
echo $a2->i; // result: 2

Can I add a function to that class that can have "visibility" of all instances of itself so I can do something like so (which I know doesn't work, but communicates my thought):

class A
{
   public $i;

   function setValue($val) {
      $this->i = $val;
   }

   function getTotal() {
      return sum($this->i); // I know sum() isn't a built-in function, but it helps explain what I want. I'm not sure if $this makes sense here too.
   }
}  

$a1 = new A;
$a1->setValue(5);
echo $a1->i; // result: 5

$a2 = new A;
$a2->setValue(2);
echo $a2->i; // result: 2

echo A::getTotal(); // returns: 7

I guess A::getTotal() means getTotal() would need to be static, but if it was static then it wouldn't then be able to "see" each class instance.

Is this type of thing possible, and what's the correct terminology I should be using?

Answer 1

No, there is no built-in instance enumeration, you will need to keep references to each instantiated object yourself. You can keep an array of instances in a static property of the class and populate it in your __construct(). You can then have a static method loop over this array and process all instances.