Rewriterule .htaccess in subfolder

Have this code in subfolder/.htaccess:

Options -MultiViews
RewriteEngine On
RewriteBase /subfolder/

RewriteRule ^chapter/([\w-]+)/?$ chapter.php?urlkey=$1 [L,NC,QSA]

Option MultiViews (see http://httpd.apache.org/docs/2.4/content-negotiation.html) is used by Apache's content negotiation module that runs before mod_rewrite and makes Apache server match extensions of files. So if /file is the URL then Apache will serve /file.html.

Also there is no need to rewrite to chapter?... you can rewrite to chapter.php?...

Your error is not related to htaccess rules.

Notice: Undefined Index

Happens when you try to access an array by a key that does not exist in the array.

A typical example for an Undefined Index notice would be check sample code below.

$data = array('foo' => '42', 'bar');
echo $data['spinach'];
echo $data[1];

Both spinach and 1 do not exist in the array, causing an to be triggered.

The solution is to make sure the index or offset exists prior to accessing that index. This may mean that you need to fix a bug in your program to ensure that those indexes do exist when you expect them to. Or it may mean that you need to test whether the indexes exist using array_key_exists or isset:

$data = array('foo' => '42', 'bar');
if (array_key_exists('spinach', $data)) {
    echo $data['spinach'];
}
else {
    echo 'No key spinach in array';
}

If you have code like:

<?php echo $_POST['message']; ?>
<form method="post" action="">
    <input type="text" name="message">
    ...

then $_POST['message'] will not be set when this page is first loaded and you will get the above error. Only when the form is submitted and this code is run a second time will the array index exist. You typically check for this with:

if ($_POST)  ..  // if the $_POST array is not empty
// or
if ($_SERVER['REQUEST_METHOD'] == 'POST') ..  // page was requested with POST

The notices above appear often when working with $_POST, $_GET or $_SESSION. For $_POST and $_GET you just have to check if the index exists or not before you use them. For $_SESSION you have to make sure you have the session started with session_start() and that the index also exists.

When removing RewriteBase it does working for me

put this in subfolder please check

Options -Indexes
RewriteEngine On

RewriteCond %{REQUEST_FILENAME} !-d 
RewriteCond %{REQUEST_FILENAME}\.php -f 
RewriteRule ^chapter/([a-z0-9]+)/?$ chapter.php?url=$1 [L,NC,QSA]

and you have to add chapter.php? instead of chapter?.