php wtf ~ php's (regular) sorting algorithm is totally unpredictable with mixed types

gistfile1.php

<?php

$array1 = array("a","b","4",5,4,"true","TRUE",true, false, "c", "d");
$array2 = array("a","b","4",5,4,"true","TRUE",true, false, "c");

sort($array1);
sort($array2);

dump($array1);
dump($array2);


function dump($var)
{
    echo '<pre><code>';
    var_dump($var);
    echo '</code></pre>';
}