<?php

class a
{
    public function getVal()
    {
        return 1;
    }

    public static function construct($n)
    {
        $a = 'a';

        do {
            $o = new $a();
            $b = get_class($o);
            $a = $b; $a++;

            eval("class $a extends $b
            {
                public function getVal()
                {
                    return parent::getVal() + 1;
                }
            }
            ");
        } while ($n !== $o->getVal());

        return $o;
    }
}

echo a::construct(38)->getVal();