function createThumbnail($imageDirectory, $imageName, $thumbDirectory, $thumbWidth)
{
$srcImg = imagecreatefromjpeg("$imageDirectory/$imageName");
$origWidth = imagesx($srcImg);
$origHeight = imagesy($srcImg);
$ratio = $origWidth / $thumbWidth;
$thumbHeight = $origHeight * $ratio;
$thumbImg = imagecreate($thumbWidth, $thumbHeight);
imagecopyresized($thumbImg, $srcImg, 0, 0, 0, 0, $thumbWidth, $thumbHeight, imagesx($thumbImg), imagesy($thumbImg));
imagejpeg($thumbImg, "$thumbDirectory/$imageName");
}
createThumbnail("img", "theFileName.jpg", "img/thumbs", 100);