potíže s uploadem souboru

<form enctype="multipart/form-data" action="" method="POST"> 
<input name="file" type="file" />
<input type="submit" value="upload" /> 
</form>
<?php
if(isset($_POST['upload'])) {
$target = "upload/"; 
$target = $target.basename( $_FILES['file']['name']) ; 
  if (file_exists($target.$_FILES["file"]["name"])) {
    echo "Soubor <strong>".$_FILES["file"]["name"]."</strong> již existuje.";
  }
  elseif ($_FILES["file"]["size"] < 10485760) {
    echo "Maximální velikost nahraného souboru je <strong>10MB</strong>.";
  }
  else { 
    if(move_uploaded_file($_FILES['file']['tmp_name'], $target)) { 
    echo "Upload: " . $_FILES["file"]["name"] . "<br />";
    echo "Type: " . $_FILES["file"]["type"] . "<br />";
    echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
    echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";
    } 
    else { 
    echo "Chyba! Soubor nebyl nahrán."; 
    } 
  }
}
?>