Helper Fonksiyonum aşşağıda ki gibidir.
Çözümü Bilen duyan var mı ?

<?php
   function USDtoTRY($cost){
    $oneYear = 60*60*24*365;
    $urls = array();
    $SiteMapURL = "http://www.tcmb.gov.tr/kurlar/today.xml";
    $DomDocument = new DOMDocument();
    $DomDocument->preserveWhiteSpace = false;
    $DomDocument->load($SiteMapURL);
    $DomNodeList = $DomDocument->getElementsByTagName('Isim');
    $DomNodeForexBuying = $DomDocument->getElementsByTagName('ForexBuying');
    $DomNodeForexSelling = $DomDocument->getElementsByTagName('ForexSelling');

    foreach($DomNodeList as $url) {
        $urls[] = $url->nodeValue;
    }

    foreach($DomNodeForexBuying as $buying) {
        $usd1[] = $buying->nodeValue;
    }

    foreach($DomNodeForexSelling as $selling) {
        $usd2[] = $selling->nodeValue;
    }
    $try = $usd2[0] * $cost;
    return $try;

}
?>

Hata Çıktısı ise