Possible file upload attack! ayuda con esto

<?
$pid = $_REQUEST['pid'];
if (isset($_FILES['file']['name'])){
// config
$dir = $_SERVER['DOCUMENT_ROOT'].'/full/'.$pid;
$uploaddir =$dir.'/';
if (file_exists($uploaddir)) {}else{mkdir($uploaddir, 0777);}
$file_types = Array ("application/msword", "application/vnd.ms-excel", "application/pdf");
//end config

$file_type = $_FILES['file']['type'];
if (in_array (strtolower ($file_type), $file_types)) {
//gets temporary file
$systemfile = $_FILES['file']['tmp_name'];
//sets destination and filename
$uploadfile = $uploaddir . $_FILES['file']['name'];

print "<pre>";
// checks if file can be set at las location
if (move_uploaded_file($_FILES['file']['tmp_name'], $uploadfile)) {
// Prints information os success
print "File is valid, and was successfully uploaded. ";
print "Here's some more debugging info:\n";
print_r($_FILES);
} else {
// Prints information on fail
print "Possible file upload attack! Here's some debugging info:\n";
print_r($_FILES);
}
print "</pre>";
} else {echo "solamente pueden cargarse archivos tipo: pdf, xls y doc.\n";}
}
?>

Possible file upload attack! Here's some debugging info:
Array
(
[file] => Array
(
[name] => sobre.pdf
[type] => application/pdf
[tmp_name] => /tmp/phpWbcU7p
[error] => 0
[size] => 265357
)

)