Shock

<?php
// $tree = generateData(10, 4, null);
// insertTreeFHRecursive($tree);
// insertTreeMPRecursive($tree);

$ids = array();
for ($i = 20; $i--;) {
    $ids[] = mt_rand(1, 111110);
}

$start = microtime(1);
foreach ($ids as $id) {
    /*
     * 0.018718957901001
     * 0.014946937561035
     * 0.018213987350464
     * 0.018930912017822
     */ getTreeByParent_FH ($id);
}
echo microtime(1) - $start , "\n";

$start = microtime(1);
foreach ($ids as $id) {
    /*
     * 0.99656295776367
     * 1.1232969760895
     * 1.3415250778198
     * 1.090959072113
     */ getTreeByParent_MP ($id);
}
echo microtime(1) - $start , "\n";