backup mysql with php

我使用这个函数使mysql备份它的工作很好，但我的问题是我有一些数据与utf-8编码在我的数据库，当使用这个函数的数据更改为"?????"我怎么能修复它?

function backup_tables($host,$user,$pass,$name,$tables = '*')
{   
    $link = mysql_connect($host,$user,$pass);
    mysql_select_db($name,$link);
    if($tables == '*')
    {
        $tables = array();
        $result = mysql_query('SHOW TABLES');
        while($row = mysql_fetch_row($result))
        {
            $tables[] = $row[0];
        }
    }
    else
    {
        $tables = is_array($tables) ? $tables : explode(',',$tables);
    }
    foreach($tables as $table)
    {
        $result = mysql_query('SELECT * FROM '.$table);
        $num_fields = mysql_num_fields($result);
        $return.= 'DROP TABLE '.$table.';';
        $row2 = mysql_fetch_row(mysql_query('SHOW CREATE TABLE '.$table));
        $return.= "'n'n".$row2[1].";'n'n";
        for ($i = 0; $i < $num_fields; $i++) 
        {
            while($row = mysql_fetch_row($result))
            {
                $return.= 'INSERT INTO '.$table.' VALUES(';
                for($j=0; $j<$num_fields; $j++) 
                {
                    $row[$j] = addslashes($row[$j]);
                    $row[$j] = ereg_replace("'n","''n",$row[$j]);
                    if (isset($row[$j])) { $return.= '"'.$row[$j].'"' ; } else { $return.= '""'; }
                    if ($j<($num_fields-1)) { $return.= ','; }
                }
                $return.= ");'n";
            }
        }
        $return.="'n'n'n";
    }
    $handle = fopen('db-backup-'.time().'-'.(md5(implode(',',$tables))).'.sql','w+');
    fwrite($handle,$return);
    fclose($handle);
}