GD Image Resizing Problem

[hearn]

I am trying to create thumbnails in ratio to a pre-defined width.

However, My images are distorted out of ratio, here is what i have, can someone give me the correct way to get the ratio for the height?

Thanks in advance!

 $src_img = imagecreatefromJPEG($path . $current["id"] . "_" . $current["title"] . "/" . $image[$a]) or die("Failed to create image"); 
                    $compression = $settings["compression"];
                    if ($settings["scaleby"]=="width") {
                        $ratio = (imagesx($src_img)/imagesy($src_img));
                        $new_width = $settings["scalevalue"];
                        $new_height = $new_width/$ratio;
                    }
                    $new_width = 100; 
                    $dst_img = imagecreatetruecolor($new_width,$new_height); 
                    imagecopyresampled($dst_img, $src_img, 0, 0, 0, 0, $new_width, $new_height, imagesx($src_img), imagesy($src_img)); 
                    imagejpeg($dst_img, $path . $current["id"] . "_" . $current["title"] . "/temp/" . $image[$a], $compression) or die("Died on call to imagejpeg() function");