http://userguide.icu-project.org/transforms/general
$ sudo aptitude install libicu-dev
First you need to enable suport for it.
<?php
$string = "glāžšķūņu rūķīši";
echo transliterator_transliterate(
"Any-Latin; NFD; [:Nonspacing Mark:] Remove; NFC; [:Punctuation:] Remove; Lower();",
$string
);
// Output: glazskunu rukisi