Something

<?php 

require_once('../config.php');


$text = ' <span lang="fr">You can search material:</span> ';

$search = '/(<(?:lang|span) lang="[a-zA-Z0-9_-]*".*?>.+?<\/(?:lang|span)>)(\s*<(?:lang|span) lang="[a-zA-Z0-9_-]*".*?>.+?<\/(?:lang|span)>)+/is';

$newtext = preg_replace_callback($search, 'multilangupgrade_impl', $text);

print_object($text);

print_object($newtext);



function multilangupgrade_impl($langblock) {
    print_object($langblock);
    $searchtosplit = '/<(?:lang|span) lang="([a-zA-Z0-9_-]*)".*?>(.+?)<\/(?:lang|span)>/is';
    preg_match_all($searchtosplit, $langblock[0], $rawlanglist);
    $return = '';
    foreach ($rawlanglist[1] as $index=>$lang) {
        $return .= '<span lang="'.$lang.'" class="multilang">'.$rawlanglist[2][$index].'</span>';
    }
    return $return;
}

?>