Záhadná matematika v php

<?php

function takCo($a, $b) {
    $r = 'a ('.gettype($a).'): '.$a.', b ('.gettype($b).'): '.$b;
    $r .= '<br>jsou ';
    $r .= ($a == $b) ? 'stejna' : 'ruzna';
    $r .= ' cisla<hr>';
    return $r;
}

echo takCo(16.65, 16.64 + 0.01); //ruzna
echo takCo(16.64, 16.63 + 0.01); //stejna
echo takCo("16.65", 16.64 + 0.01); //ruzna
echo takCo("16.64", 16.63 + 0.01); //stejna
echo takCo((int) 16.1, (int) 16 + 0.1); //ruzna
echo takCo((int) 16.1, (int) (16 + 0.1)); //stejna