preg_replace multiple-replace bugs
===

I try to make a function for rename file after upload but this function bugs and i don't understand..

This is a simple example code :

    echo $pathinfo["filename"]."<br/>";
    $pathinfo["filename"] = preg_replace('/[ÝŶŸỲỸỶỴ]/', "Y", $pathinfo["filename"]);
    echo $pathinfo["filename"]."<br/>";

And the result : 

    JPEG xè.w_.a(m)aaỶle_oui_
    JPEG xY�.w_.a(m)aaYYYle_oui_

è are transformed ?? And Ỷ => YYY ??

I realy don't understand why i don't have 'JPEG xè.w_.a(m)aaYle_oui_' ??

Thank you all