Php static variable initialization

Php member variables can be initialized at the same time as they are declared, but only scalar variables can be initialized. For example:
Class {
Public $ f1 = 'xxxx ';
Static public $ f2= 100;
}


If you want to assign a variable to an object, you can only initialize the variable in the constructor. for example:
Class {
Private $ child;
Public function _ construct (){
$ This-> child = new B ();
}
}


However, php does not have anything similar to the static constructor/static block in java, so there is no proper time to initialize it.


There are still solutions for common members, such:
Class {
Static public $ child;
}
A: $ child = new B ();


There seems to be no clean method for private members. you can only do this:
Class {
Static private $ child;
Static public initialize (){
Self: $ child = new B ();
}
}
A: initialize ();