php从上传的文件创建缩略图_PHP

php从上传的文件创建缩略图
<? 
if ($_REQUEST['action']=="add"){ 
$userfile = $HTTP_POST_FILES['photo']['tmp_name']; 
$userfile_name = $HTTP_POST_FILES['photo']['name']; 
$userfile_size = $HTTP_POST_FILES['photo']['size']; 
$userfile_type = $HTTP_POST_FILES['photo']['type']; 
/////////////////////////  
//GET-DECLARE DIMENSIONS // 
$dimension = getimagesize($userfile); 
$large_width = $dimension[0]; // GET PHOTO WIDTH 
$large_height = $dimension[1]; //GET PHOTO HEIGHT 
$small_width = 120; // DECLARE THUMB WIDTH 
$small_height = 90; // DECLARE THUMB HEIGHT 
///////////////////////// 
//CHECK SIZE  // 
if ($userfile_size>102400){ 
     $error=1; 
     $msg = "The photo is over 100kb. Please try again."; 
} 
//////////////////////////////// 
// CHECK TYPE (IE AND OTHERS) // 
if ($userfile_type="image/pjpeg"){ 
    if ($userfile_type!="image/jpeg"){ 
       $error=1; 
       $msg = "The photo must be JPG"; 
    } 
} 
////////////////////////////// 
//CHECK WIDTH/HEIGHT // 
if ($large_width!=600 or$large_height!=400){ 
$error=1; 
$msg = "The photo must be 600x400 pixels"; 
} 
/////////////////////////////////////////// 
//CREATE THUMB / UPLOAD THUMB AND PHOTO /// 
if ($error<>1){ 
     
    $image = $userfile_name; //if you want to insert it to the database 
    $pic = imagecreatefromjpeg($userfile); 
    $small = imagecreatetruecolor($small_width,$small_height); 
    imagecopyresampled($small,$pic,0,0,0,0, $small_width, $small_height, $large_width, $large_height); 
    if (imagejpeg($small,"path/to/folder/to/upload/thumb".$userfile_name, 100)){     
        $large = imagecreatetruecolor($large_width,$large_height); 
    imagecopyresampled($large,$pic,0,0,0,0, $large_width, $large_height, $large_width, $large_height); 
        if (imagejpeg($large,"path/to/folder/to/upload/photo".$userfile_name, 100)) 
      {} 
           else {$msg="A problem has occured. Please try again."; $error=1;} 
    } 
    else { 
      $msg="A problem has occured. Please try again."; $error=1; 
    } 
} 
////////////////////////////////////////////// 
/// If everything went right a photo (600x400) and 
/// a thumb(120x90) were uploaded to the given folders 
} 
?> 
<html><head><title>create thumb</title></head>
<body>
<form name="form1" enctype="multipart/form-data" action="thisfile.php?action=add" method="post">
Select Photo: <input type="file" name="photo">
<input type="submit" name="submit" value="CREATE THUMB AND UPLOAD">
</form>
</body
</html>