我有缩略图代码，它适用于 gif、png 和 jpeg 文件，但不适用于 jpg。
请帮助我如何使它适用于jpg。
我没有收到任何错误，日志文件中也没有任何内容。
function create_thumb($src,$dest,$desired_width = false, $desired_height = false){
if (!$desired_height&&!$desired_width) return false;
$fparts = pathinfo($src);
$ext = strtolower($fparts['extension']);
if (!in_array($ext,array('gif','jpg','png','jpeg'))) return false;
if ($ext == 'gif') $resource = imagecreatefromgif($src);
else if ($ext == 'png') $resource = imagecreatefrompng($src);
else if ($ext == 'jpg' || $ext == 'jpeg') $resource = imagecreatefromjpeg($src);
$width = imagesx($resource);
$height = imagesy($resource);
if(!$desired_height) $desired_height = floor($height*($desired_width/$width));
if(!$desired_width) $desired_width = floor($width*($desired_height/$height));
$virtual_image = imagecreatetruecolor($desired_width,$desired_height);
imagecopyresized($virtual_image,$resource,0,0,0,0,$desired_width,$desired_height,$width,$height);
$fparts = pathinfo($dest);
$ext = strtolower($fparts['extension']);
if (!in_array($ext,array('gif','jpg','png','jpeg')))
$ext = 'jpg';$dest = $fparts['dirname'].'/'.$fparts['filename'].'.'.$ext;
if ($ext == 'gif') imagegif($virtual_image,$dest);
else if ($ext == 'png') imagepng($virtual_image,$dest,1);
else if ($ext == 'jpg' || $ext == 'jpeg') imagejpeg($virtual_image,$dest,72);
return array( 'width' => $width, 'height' => $height, 'new_width' => $desired_width, 'new_height'=> $desired_height, 'dest' => $dest ); }