Troubleshooting Admin_Notice

Question

I have this code at the top of a plugin:

 function my_mwe_admin_notice(){
    echo '<div class="notice notice-error">';
    echo '<h1>Notice this.</h1>';
    echo '</div>';
 }
add_action( 'admin_notices', 'my_mwe_admin_notice' );

Where and when is this notice supposed to appear?

I can't find it.

Have also tried adding global $pagenow and if ( 'plugins.php' == $pagenow ) { // also index.php, etc...

What am I missing?

Answer 1

Yup. I threw my test code in the top of the Hello Dolly plugin and there was the notice.

That's when I remembered that I was calling it within a namespace:

So needed to referenced that so the WP action could access it:

namespace My_Plugin;

function my_mwe_admin_notice(){
    echo '<div class="notice notice-error">';
    echo '<h1>Notice this.</h1>';
    echo '</div>';
 }
add_action( 'admin_notices', __NAMESPACE__ . '\\my_mwe_admin_notice' );