prova cosi
Codice PHP:
<?php
if(isset($_POST['submit'])){
$dirname = $_POST['dirname'];
mkdir("$dirname/","0755");
}
else
{echo "
<html>
<body>

<form name='form1' method='post' action='form.php'>

Directory Name:<input type='text' name='dirname'>
<input type='submit' name='submit' value='Crea'>

</form>

</body>
</html>";
}
?>