That gist demonstrate simply when use is_callable / __call instead of method_exist to avoid all visibility problems induced by method_exist().

method_exist Vs is_callable Vs __call

<?php

class LaBase {
//    private function foobar() {return true;}
//    public function foobar() {return true;}
}

class NoMagic extends LaBase {
    function isParentFoobarCallable() {
        return is_callable('parent::foobar');
    }
    
    function methodExists(){return method_exist($this, 'foobar');}
}

class Magic extends NoMagic {                
    function __call($method, $args) {}
}

$nomagic = new NoMagic();
var_dump($nomagic->isParentFoobarCallable());

$magic = new Magic();
var_dump($magic->isParentFoobarCallable());;
//var_dump($magic->methodExists());