$array = array("Alpha", "Foo", "Bar", "Meh");
usort($array, function ($a, $b) {
    $last = "Alpha";
    if ($a == $b) return 0;
    if ($a < $b || $b == $last) return -1;
    if ($a > $b || $a == $last) return 1;
});
print_r($array);