PHP按比例调整大小

可能重复：
计算调整大小的图像大小比率

所以我有一个简单的上传脚本，可以调整上传的图片的大小，我想强制调整宽度大小，让高度自动成比例。

这是我的上传脚本：

if (isset($_POST['upload'])) {
        $dirupload = "../images/";
        $dirupload = $dirupload . basename( $_FILES['image-upload']['name']);
        $useless = $_POST['useless'];
        $imageupload = ($_FILES['image-upload']['name']);
        $uploadedfileupload = $_FILES['image-upload']['tmp_name'];
        $uploadedfiletypeupload = $_FILES['image-upload']['type']; 
        $query_add="SELECT * FROM produits ORDER BY position";
        $result_add=mysql_query($query_add);
        $num_add=mysql_num_rows($result_add);
        $add_add=$num_add+1;
        if (!($uploadedfiletypeupload =="image/pjpeg" OR $uploadedfiletypeupload =="image/jpeg" OR $uploadedfiletypeupload =="image/jpg")){
            echo "L'image doit être en .jpg ou .jpeg";
        }else if (move_uploaded_file($_FILES['image-upload']['tmp_name'], $dirupload)){     
            $sql="INSERT INTO produits (position) VALUES ('$add_add')";
            if (!mysql_query($sql,$con)){
                die('Error: ' . mysql_error());
            }       

            $newnameupload = "../images/produit" . mysql_insert_id() . ".jpg";
            rename ("../images/$imageupload","$newnameupload");    
            $orig_imageupload = imagecreatefromjpeg("../image/$newnameupload");
            $sm_imageupload = imagecreatetruecolor(274,219);
            imagecopyresampled($sm_imageupload,$orig_imageupload,0,0,0,0,274,219,imagesx($orig_imageupload),imagesy($orig_imageupload));
            imagejpeg($sm_imageupload, $newnameupload, 100);
        }else{
            echo "Un probleme est survenue";
        }
    }

有什么想法可以让它发挥作用吗？（是的，我现在已经在脚本中设置了高度）

提前感谢！