<?php

class A() {
    private $methods = array();
    private function defaultMethods() {
        $this->methods['func1'] = function() { return "Foo"; };
    }
    public function __construct() {
        $this->defaultMethods();
    }
    public function __construct(array $funcs) {
        $this->defaultMethods();
        foreach($funcs as $key => $val) {
            $this->methods[$key] = $val;
        }
    }
    public function __call($name, $arguments) {
        call_user_func_array($this->methods[$name], $arguments);
    }
}

$a = new A();

echo $a->func1();

$b = new A(array('func1' => function(){ return "Bar";}));

echo $b->func1();

?>