Why isn’t admin_notices displaying my text? [Simple Plugin, Beginner]

var_dump($paths); shows that the your $paths variable is an empty string. It’s not showing anything because there is nothing to show.

Since you seem like you’re trying to find all the plugins, you should have a look at get_plugins. glob is going to be relative to the current working directory (with will vary depending on your server setup) and is_plugin_active active takes a plugin_basename.

get_plugins will return an associative array with the plugin basenames as keys as the file header data as the values (in an array).

A few other notes:

admin_notices does not automagically format your notices to look pretty. You can wrap it your notice with <div class="error"> or <div class="updated"> to do that.

Always give your functions a unique prefix or put them in a namespace (PHP 5.3+ only).

Revised code:

<?php
add_action('admin_notices', 'wpse72637_show_names');
function wpse72637_show_names()
{                  
    $paths = array();

    foreach(get_plugins() as $p_basename => $plugin)
    {
        $paths[] = "{$plugin['Name']}: " .
            (is_plugin_active($p_basename) ? 'Active' : 'Disabled');
    }

    echo '<div class="updated"><p>', implode(' --- ', $paths), '<p></div>';
}