在特定路径创建文件夹

I'm pretty new with PHP so the question could seem easy. I have an html file with an input with these attributes:

<td width="30%">
<input type="text" id="prog1" name="prog1" style="width:150px">
</td>

I must create a new folder on my server inside another folder called wars that already exists. The new folder's name is stored on that input. For example, if the input's text is "home", my PHP script is gonna make a folder here: wars/home.

<?
$val = $_REQUEST['prog2'];
mkdir("/wars/".$val, 0777);
?>

This is my code but it's not working because inside the main folder wars I can't find home. Do you have any suggestion?

The main issue is a typo:

$val = $_REQUEST['prog2'];

Your form only has <input name="prog1" .... However, you also have to seriously consider sanitizing your variables:

$val = $_REQUEST['prog1'];
// only allow alphabetical characters
if (preg_match('/^[a-z]+$/', $val)) {
    mkdir("/wars/$val", 0777);
}

Lastly, consider using $_POST instead of $_REQUEST unless you never know where the variable is going to come from.

Try:

<?php
$val = $_POST['prog1'];
mkdir("/wars/".$val, 0777);
?>

notice the wrong input prog1 !== prog2 attribute, also learn to do some simple debuging, like:

<?php echo '<pre>'.print_r($_POST,true).'</pre>'; ?>

Also enable error reporting on development.

<?php error_reporting(E_ALL); ?>