Example of a PHP function to resize an image

function resize($im, $dst_width, $dst_height)
{
   $width = imagesx($im);
   $height = imagesy($im);

   $newImg = imagecreatetruecolor($dst_width, $dst_height);

   $white = imagecolorallocate($newImg, 255, 255, 255);
   imagefill($newImg,0,0,$white);
   
   imagecopyresampled($newImg, $im, 0, 0, 0, 0, $dst_width, $dst_height, $width, $height);

   return $newImg;
}

$image   = ImageCreateFromJpeg($uploaded_file);

$tn = resize($image, $modwidth, $modheight);

imagejpeg($tn, $save_file_name,95);