ok l'ho fatto ma niente non riesco a creare le foto

<?php
$car=mkdir("./foto/foto1", 0700);

if(isset($_POST['action']) and $_POST['action'] == 'upload')
{
if(isset($_FILES['user_file']))
{
$file = $_FILES['user_file'];
if($file['error'] == UPLOAD_ERR_OK and is_uploaded_file($file['tmp_name']))
{
move_uploaded_file($file['tmp_name'], $car.$file['name']);
$fp=fopen('listanomi.txt','a');
fwrite($fp,$file['name']."-");
fclose($fp);
}
}
}
print "_________".$car."__________".$file['name'];


?>

sto impazzendo non riesco a capire come si usa mkdir