odstranění diakritiky ve vyhledávání

Nějak mi nefunguje zbavení se diakritiky, nevíte proč?

<?
function upravstr($nazev){
$diakritika = Array(
'ä' => 'a',
'Ä' => 'a',
'á' => 'a',
'Á' => 'a',
'č' => 'c',
'Č' => 'c',
'ć' => 'c',
'Ć' => 'c',
'ď' => 'd',
'Ď' => 'd',
'ě' => 'e',
'Ě' => 'e',
'é' => 'e',
'É' => 'e',
'ë' => 'e',
'Ë' => 'e',
'í' => 'i',
'Í' => 'i',
'ľ' => 'l',
'Ľ' => 'l',
'ń' => 'n',
'Ń' => 'n',
'ň' => 'n',
'Ň' => 'n',
'ó' => 'o',
'Ó' => 'o',
'ö' => 'o',
'Ö' => 'o',
'ř' => 'r',
'Ř' => 'r',
'ŕ' => 'r',
'Ŕ' => 'r',
'š' => 's',
'Š' => 's',
'ś' => 's',
'Ś' => 's',
'ť' => 't',
'Ť' => 't',
'ú' => 'u',
'Ú' => 'u',
'ü' => 'u',
'Ü' => 'u',
'ý' => 'y',
'Ý' => 'y',
'ž' => 'z',
'Ž' => 'z',
'ź' => 'z',
'Ź' => 'z'
);
$nazevx = strtr($nazev,$diakritika);
$nazevx = strtolower($nazevx);
return $nazevx;
}
$_GET['word'] = upravstr(htmlspecialchars($_GET['word'],ENT_QUOTES));
?>
<?php
mysql_connect("***","***","***");
mysql_select_db("***");

$sql = "SELECT *,MATCH (jmeno, popis) AGAINST ('$_GET[word]' IN BOOLEAN MODE) relevancy FROM
produkty WHERE MATCH (jmeno, popis) AGAINST ('$_GET[word]' IN BOOLEAN MODE) ORDER BY
relevancy DESC";




$q = mysql_query ($sql);
echo mysql_error();
$n = mysql_num_rows($q);

?>
<?php echo $n; ?> záznamy/ů:
<br />
<?php

while ($arr = mysql_fetch_array($q)) {
?>

<a href="<?echo "zobraz_kontakty.php?id=$arr[id]";?>">

<li><?echo $arr["jmeno"];?>
<?echo " &nbsp;&nbsp;>&nbsp;&nbsp; "; ?>
<?echo $arr["popis"];?>
</li>
</a>
<?

}

?>
<br />
<?
mysql_close();

?>