[php] How to override trait function and call it from the overridden function?

If the class implements the method directly, it will not use the traits version. Perhaps what you are thinking of is:

trait A {
    function calc($v) {
        return $v+1;
    }
}

class MyClass {
    function calc($v) {
        return $v+2;
    }
}

class MyChildClass extends MyClass{
}

class MyTraitChildClass extends MyClass{
    use A;
}

print (new MyChildClass())->calc(2); // will print 4

print (new MyTraitChildClass())->calc(2); // will print 3

Because the child classes do not implement the method directly, they will first use that of the trait if there otherwise use that of the parent class.

If you want, the trait can use method in the parent class (assuming you know the method would be there) e.g.

trait A {
    function calc($v) {
        return parent::calc($v*3);
    }
}
// .... other code from above
print (new MyTraitChildClass())->calc(2); // will print 8 (2*3 + 2)

You can also provide for ways to override, but still access the trait method as follows:

trait A {
    function trait_calc($v) {
        return $v*3;
    }
}

class MyClass {
    function calc($v) {
        return $v+2;
    }
}


class MyTraitChildClass extends MyClass{
    use A {
      A::trait_calc as calc;
    }
}


class MySecondTraitChildClass extends MyClass{
    use A {
      A::trait_calc as calc;
    }

    public function calc($v) {
      return $this->trait_calc($v)+.5;
    }
}


print (new MyTraitChildClass())->calc(2); // will print 6
echo "\n";
print (new MySecondTraitChildClass())->calc(2); // will print 6.5

You can see it work at http://sandbox.onlinephpfunctions.com/code/e53f6e8f9834aea5e038aec4766ac7e1c19cc2b5