jpg upload problem in firefox

i have problem uploading jpg in Firefox ;
here is my code

if($_FILES){
foreach($_FILES as $key => $file){
$upload->set("name",$file["name"]); // Uploaded file name.
$upload->set("type",$file["type"]); // Uploaded file type.
$upload->set("tmp_name",$file["tmp_name"]); // Uploaded tmp file name.
$upload->set("error",$file["error"]); // Uploaded file error.
$upload->set("size",$file["size"]); // Uploaded file size.
$upload->set("fld_name",$key); // Uploaded file field name.
$upload->set("max_file_size",72960); // Max size allowed for uploaded file in bytes = 40 KB.
$upload->set("supported_extensions",array("gif" => "image/gif" ,"jpg" => "image/jpeg" ,"jpg" => "image/pjpeg" ,"jpeg" => "image/jpeg", "jpg" => "image/jfif" ,"png" => "image/x-png")); // Allowed extensions and types for uploaded file.
$upload->set("randon_name",true); // Generate a unique name for uploaded file? bool(true/false).
$upload->set("replace",FALSE); // Replace existent files or not? bool(true/false).
$upload->set("file_perm",0444); // Permission for uploaded file. 0444 (Read only).
$upload->set("dst_dir", "../upload_dir/"); // Destination directory for uploaded files.

$result = $upload->moveFileToDestination(); // $result = bool (true/false). Succeed or not.
}