<?php
$arr = array("4.0.1", "trunk", "branch", "4.1.0", "4.0.3", "1.2", "1.31", "1.10", "1.4.5");
natsort($arr);
$count = count($arr);
$alpha = array();
$new_arr = array();
for($i = 0; $i < $count; $i++) {
    if(!is_numeric(str_replace('.', '', $arr[$i]))) {
        $alpha[] = $arr[$i];
    } else {
        $new_arr[] = $arr[$i];
    }
    $arr[$i] = null;
}
rsort($new_arr);
sort($alpha);
$new_arr = array_merge($new_arr, $alpha);
var_dump($new_arr);
?>