Yet another single-line mb_trim() function

<?php
function mb_trim($string, $trim_chars = '\s'){
    return preg_replace('/^['.$trim_chars.']*(?U)(.*)['.$trim_chars.']*$/u', '\\1',$string);
}
$string = '           "some text."      ';
echo mb_trim($string, '\s".');
//some text
?>