<?php

trait Foo
{
    private function inTrait(): void { echo "foobar\n"; }
}

class A {
    use Foo;
    
    public function bar(): void {
        $this->inTrait();
    }        
}

class B extends A {    
    use Foo;

    function baz(): void
    {
        $this->inTrait();
    }
}

$b = new B();
$b->baz();