Можно использовать такую функцию, несколько букв я показал для примера, остальные допишите сами.
<?php
function Letter_Replase(){
global $l_r;
$_0 = str_replace("ü","у", $l_r);
$_1 = str_replace("Ü","У", $_0);
$_2 = str_replace("ö","о", $_1);
$_3 = str_replace("Ö","O", $_2);
$_4 = str_replace("ğ","г", $_3);
$_5 = str_replace("Ğ","Г", $_4);
$_6 = str_replace("ə","e", $_5);
$_7 = str_replace("Ə","E", $_6);
$_8 = str_replace("ı","и", $_7);
$_9 = str_replace("I","И", $_8);
$_10 = str_replace("ç","ч", $_9);
$_11 = str_replace("Ç","Ч", $_10);
$_12 = str_replace("ş","ш", $_11);
$_13 = str_replace("Ş","Ш", $_12);
$_14 = str_replace("'","", $_13);
$_15 = str_replace(",","", $_14);
$_16 = str_replace('"',"", $_15);
$_17 = str_replace('`',"", $_16);
$_18 = str_replace('-',"", $_17);
$_19 = str_replace('--',"", $_18);
$_20 = str_replace('---',"", $_19);
$_21 = str_replace(':',"", $_20);
$_22 = str_replace(' ',"-", $_21);
$_23 = str_replace(';',"-", $_22);
$_24 = str_replace('_',"", $_23);
$_25 = str_replace('“',"", $_24);
$_26 = str_replace('”',"", $_25);
$_27 = str_replace('!',"", $_26);
$_28 = str_replace('?',"", $_27);
$_29 = str_replace('@',"", $_28);
$_30 = str_replace('$',"", $_29);
$_31 = str_replace('%',"", $_30);
$_32 = str_replace('^',"", $_31);
$_33 = str_replace('&',"", $_32);
$_34 = str_replace('*',"", $_33);
$_35 = str_replace('=',"", $_34);
$_36 = str_replace('+',"", $_35);
$_37 = str_replace('/',"", $_36);
$_38 = str_replace("\/","", $_37);
$_39 = str_replace('|',"", $_38);
$_40 = str_replace('[',"", $_39);
$_41 = str_replace(']',"", $_40);
$_42 = str_replace('>',"", $_41);
$_43 = str_replace('<',"", $_42);
$_44 = preg_replace('/{}[(][)][.]/', '', $_43);
echo mb_strtolower($_44);
}
?>