Compress and RESCALE uploaded image

I have a function that uploads files up to 8MB but now I also want to compress or at least rescale larger images, so my output image won't be any bigger than 100-200 KB and 1000x1000px resolution. How can I implement compress and rescale (proportional) in my function?

function uploadFile($file, $file_restrictions = '', $user_id, $sub_folder = '') {
    global $path_app;
    $new_file_name    = generateRandomString(20);

    if($sub_folder != '') {
        if(!file_exists('media/'.$user_id.'/'.$sub_folder.'/')) {
            mkdir('media/'.$user_id.'/'.$sub_folder, 0777);
        }
        $sub_folder = $sub_folder.'/';
    }
    else {
        $sub_folder = '';
    }

    $uploadDir  = 'media/'.$user_id.'/'.$sub_folder;
    $uploadDirO = 'media/'.$user_id.'/'.$sub_folder;
    $finalDir   = $path_app.'/media/'.$user_id.'/'.$sub_folder;

    $fileExt    = explode(".", basename($file['name']));
    $uploadExt  = $fileExt[count($fileExt) - 1];
    $uploadName = $new_file_name.'_cache.'.$uploadExt;
    $uploadDir  = $uploadDir.$uploadName;

    $restriction_ok = true;
    if(!empty($file_restrictions)) {
        if(strpos($file_restrictions, $uploadExt) === false) {
            $restriction_ok = false;
        }
    }
    if($restriction_ok == false) {
        return '';
    }
    else {
        if(move_uploaded_file($file['tmp_name'], $uploadDir)) {
            $image_info     = getimagesize($uploadDir);
            $image_width    = $image_info[0];
            $image_height   = $image_info[1];

            if($file['size'] > 8000000) {
                unlink($uploadDir);
                return '';
            }
            else {
                $finalUploadName    = $new_file_name.'.'.$uploadExt;
                rename($uploadDirO.$uploadName, $uploadDirO.$finalUploadName);

                return $finalDir.$finalUploadName;
            }
        }
        else {
            return '';
        }
    }
}