How does PHP 4 handle inheritance of constructors in classes?

In PHP 4, constructors are not inherited by child classes automatically. To ensure that constructors are inherited in child classes, you need to explicitly call the parent constructor within the child constructor using the `parent::__construct()` syntax.

class ParentClass {
    public function __construct() {
        echo "Parent constructor called";
    }
}

class ChildClass extends ParentClass {
    public function __construct() {
        parent::__construct();
        echo "Child constructor called";
    }
}

$child = new ChildClass();