WordPress MU

Hello,
I found, a few years ago (already :) ), a pretty useful script that allows to have a plugin directory that is only available to me.

In mu-plugin, i had this file my-plugin.php

<?php
define( 'MAINPLUGINDIR', 'wp-content/my-plugins' );
if ( $blog_id == 1 ) {
$plugins2 = glob( ABSPATH . MAINPLUGINDIR . '/*.php' );
if( is_array( $plugins2 ) ) {
foreach ( $plugins2 as $plugin2 ) {
if( is_file( $plugin2 ) )
include_once( $plugin2 );
}
}
}
?>

That allowed me to have a my-plugins dir, which is useful to test plugin first, but also to have only plugins not in mu-plugin but only for me.

Why doesn't this little hack work anymore since I upgraded ?

Thanks