Static strain gauge php static variable initialization

For example:
class A {
public $f1 = 'xxxx';
static public $f2 = 100;
}
If you want to assign a variable to an object, it can only be initialized in the constructor, for example:
class A {
private $child;
public function __construct() {
$this->child = new B();
}
}
But there is nothing similar to the static constructor/static block in java in php, just There is no suitable time to initialize it.
There are solutions for shared members, for example:
class A {
static public $child;
}
A::$child = new B();
There seems to be no clean method for private members. You can only do this:
class A {
static private $child;
static public initialize() {
self::$child = new B();
}
}
A::initialize();

The above introduces the initialization of static strain gauge PHP static variables, including the content of static strain gauge. I hope it will be helpful to friends who are interested in PHP tutorials.