Upload de imagens para o servidor com php (simples)

 <?php 

if (isset($_POST["submit"])) 
 { 
  $uploadpath = "imagens/"; 
  $uploadpath = $uploadpath.basename($_FILES["imgfile"]["name"]); 
  if (!move_uploaded_file($_FILES["imgfile"]["tmp_name"], $uploadpath)) 
   die("Ocorreu um erro ao enviar a imagem, tente novamente!"); 
  $image_name = "imagens/".$_FILES["imgfile"]["name"]; 
  list($width,$height) = getimagesize($image_name); 
  $new_image_name = "imagens/thumb_".$_FILES["imgfile"]["name"]; 
  if ($width > $height) 
   { 
    $ratio = (250/$width); 
    $new_width = round($width*$ratio); 
    $new_height = round($height*$ratio); 
   } 
  else 
   { 
    $ratio = (250/$height); 
    $new_width = round($width*$ratio); 
    $new_height = round($height*$ratio); 
   } 
  $image_p = imagecreatetruecolor($new_width,$new_height); 
$img_ext = $_FILES['imgfile']['type']; 
if (img_ext == "image/jpg" || img_ext == "image/jpeg") { 
$image = imagecreatefromjpg($image_name); 
} else if ($img_ext == "image/png") { 
$image = imagecreatefrompng($image_name); 
} else if ($img_ext == "image/gif") { 
$image = imagecreatefromgif($image_name); 
} else { 
die('o formato da imagem não é válido'); 
} 

imagecopyresampled($image_p,$image,0,0,0,0,$new_width,$new_height,$width,$height); 
imagejpeg($image_p,$new_image_name,100); 
   echo("Imagm enviada com sucesso!"); 
 } 

echo <<<TEXT 
<form method="post" enctype="multipart/form-data"> 
<h1>Upload de imagens com php</h1> 
Seleccione um ficheiro a enviar:<br /> 
<input type="file" name="imgfile" /> 
<br /> 
<input type="submit" name="submit" value="Enviar Imagem" /> 
</form> 
TEXT; 

?>