<?php
$String = "àäåæËÎÏÐðÑ×÷ØÝÞßdvdá";
$String = preg_replace("/([^a-zà-úA-ZÀ-Ú ]|[äåæËÎÏÐðÑ×÷ØÝÞß])/u", "", $String);
echo $String;
PD9waHAKCiRTdHJpbmcgPSAiw6DDpMOlw6bDi8OOw4/DkMOww5HDl8O3w5jDncOew59kdmTDoSI7CgokU3RyaW5nICA9IHByZWdfcmVwbGFjZSgiLyhbXmEtesOgLcO6QS1aw4Atw5ogXXxbw6TDpcOmw4vDjsOPw5DDsMORw5fDt8OYw53DnsOfXSkvdSIsICIiLCAkU3RyaW5nKTsKCmVjaG8gJFN0cmluZzsK