如何在php中使用反射作为回调

I have one class

   Class Mainclass{}

And another class which is

   Class Childclass extends Mainclass{}

Now i want to write callback in Mainclass which check if child class found with method, merge value and return?

How can i achieve using reflection?

One easy way would be to create an interface containing that method

interface XYZ
{
    public function myMethod();
}

And make your child class implement it

class Childclass extends Mainclass implements XYZ
{
    public function myMethod()
    {
        //actual implementation
    }
}

Afterwards, your main class can easily check if it is implementing that interface:

class Mainclass
{
    public function whatever()
    {
        if ($this instanceof XYZ)
        {
            $this->myMethod();
        }
    }
}

Now, I'm fairly sure it would work but I really think this is bad design: a parent class should never depend on the implementation of its child classes. However since I don't know the context in which you're working, I'll leave this here and hope it helps you anyway.