Help with file uploading in PHP

[azegurb]

Hi
I have took from internet
PHP script that uploads images to the host

<form name="upload-form" id="upload-form" method="post" action="./upload.php" enctype="multipart/form-data"> 
  <input type="hidden" name="MAX_FILE_SIZE" value="30000"> 
  <fieldset> 
  <legend>File upload:</legend> 
  <dl> 
    <dt> 
      <label for="file">File:</label> 
    </dt> 
    <dd> 
      <input tabindex="1" accesskey="b" name="file" type="file" id="file" /> 
    </dd> 
  </dl> 
  <input tabindex="2" accesskey="l" type="submit" name="cmdupload" value="Upload" /> 
  </fieldset> 
</form>

PHP-code below



<?php
$uploaddir = "upload/"; //Upload directory: needs write premissions
$log = "uploadlog.txt"; // Upload LOG file
// what file types do you want to disallow?
$blacklist = array(".php", ".phtml", ".php3", ".php4", ".php5", ".exe", ".js",".html", ".htm", ".inc");
 // allowed filetypes
$allowed_filetypes = array('.jpg','.gif','.bmp','.png');
if (!is_dir($uploaddir)) {
	die ("Upload directory does not exists.");
}
if (!is_writable($uploaddir)) {
	die ("Upload directory is not writable.");
}
if ($_POST['cmdupload'])
{
$ip = trim($_SERVER['REMOTE_ADDR']);
	if (isset($_FILES['file']))
	{
		if ($_FILES['file']['error'] != 0)
		{
			switch ($_FILES['file']['error'])
			{
				case 1:
					print 'The file is to big.'; // php installation max file size error
					exit;
					break;
				case 2:
					print 'The file is to big.'; // form max file size error
					exit;
					break;
				case 3:
					print 'Only part of the file was uploaded';
					exit;
					break;
				case 4:
					print 'No file was uploaded</p>';
					exit;
					break;
				case 6:
					print "Missing a temporary folder.";
					exit;
					break;
				case 7:
					print "Failed to write file to disk";
					exit;
					break;
				case 8:
					print "File upload stopped by extension";
					exit;
					break;
			}
		} else {
			foreach ($blacklist as $item)
			{
				if (preg_match("/$item\$/i", $_FILES['file']['name']))
				{
					echo "Invalid filetype !";
					 	$date = date("m/d/Y");
						$time = date("h:i:s A");
						$fp = fopen($log,"ab");
						fwrite($fp,"$ip | ".$_FILES['file']['name']." | $date | $time | INVALID TYPE"."\r\n");
						fclose($fp);
					unset($_FILES['file']['tmp_name']);
					exit;
				}
			}
			// Get the extension from the filename.
			$ext = substr($_FILES['file']['name'], strpos($_FILES['file']['name'],'.'), strlen($_FILES['file']['name'])-1);
   			// Check if the filetype is allowed, if not DIE and inform the user.
   			if(!in_array($ext,$allowed_filetypes)){
						$date = date("m/d/Y");
						$time = date("h:i:s A");
						$fp = fopen($log,"ab");
						fwrite($fp,"$ip | ".$_FILES['file']['name']." | $date | $time | INVALID TYPE"."\r\n");
						fclose($fp);
	  					die('The file you attempted to upload is not allowed.');
			}
			if (!file_exists($uploaddir . $_FILES["file"]["name"]))
			{
				// Proceed with file upload
				if (is_uploaded_file($_FILES['file']['tmp_name']))
				{
					//File was uploaded to the temp dir, continue upload process
					if (move_uploaded_file($_FILES['file']['tmp_name'], $uploaddir . $_FILES['file']['name']))
					{
						// uploaded file was moved and renamed succesfuly. Display a message.
						echo "Upload successful !";
						// Now log the uploaders IP adress date and time
						$date = date("m/d/Y");
						$time = date("h:i:s A");
						$fp = fopen($log,"ab");
						fwrite($fp,"$ip | ".$_FILES['file']['name']." | $date | $time | OK"."\r\n");
						fclose($fp);
					} else {
						echo "Error while uploading the file, Please contact the webmaster.";
						unset($_FILES['file']['tmp_name']);
					}
				} else {
					//File was NOT uploaded to the temp dir
					switch ($_FILES['file']['error'])
					{
						case 1:
							print 'The file is to big.'; // php installation max file size error
							break;
						case 2:
							print 'The file is to big.'; // form max file size error
							break;
						case 3:
							print 'Only part of the file was uploaded';
							break;
						case 4:
							print 'No file was uploaded</p>';
							break;
						case 6:
							print "Missing a temporary folder.";
							break;
						case 7:
							print "Failed to write file to disk";
							break;
						case 8:
							print "File upload stopped by extension";
							break;
					}
				}
			} else {
				echo "Filename already exists, Please rename the file and retry.";
				unset($_FILES['file']['tmp_name']);
			}
		}
	} else {
		// user did not select a file to upload
		echo "Please select a file to upload.";
	}
} else {
	// upload button was not pressed
	header("Location: uploadform.php");
}
?>

I do it step by step in instructions
but when i want to upload a JPG image it says error occured
pls help me to eliminate this problem
sometimes it says pls select file
but i choose an image which i want
then it says the same error
thanks for attention