How to use relative path with my plugins folders?

Question

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Don’t use a plugin folder (or a theme) for this. Maybe your plugin doesn’t have an Upgrade feature and nothing will be overwritten. But the best practice is to use a folder in /wp-content root or inside /wp-content/uploads.

In /wp-content/my-images:

$test = glob( WP_CONTENT_DIR . '/my-images/*.png');

In /wp-content/uploads/my-images:

$up_dir = wp_upload_dir();
$test = glob( $up_dir['basedir'] . '/images/*.png');