//**************************************************************************************
//**************************************************************************************
//********** DISPLAY WARNING IN WP ADIN AREA IF REQUIRED PLUGINGS ARE MISSING **********
//**************************************************************************************
//**************************************************************************************
add_action('admin_init', 'my_plugin_check_prerequisites_are_installed');        //If using namespace: '\MyNamespace\my_plugin_check_prerequisites_are_installed'
function my_plugin_check_prerequisites_are_installed()
{
  $plugin_slug = 'required_plugin_name/required_plugin_name.php'; // Change this to the actual plugin slug

  if (!is_plugin_active($plugin_slug))      //Must be installed and active for a True response
      add_action('admin_notices', 'my_plugin_check_prerequisites_warn_not_installed');        //If using namespace: '\MyNamespace\my_plugin_check_prerequisites_warn_not_installed'
}

function my_plugin_check_prerequisites_warn_not_installed()
{
  ?>
  <div class="notice notice-error">
      <p><strong>Warning:</strong>Plugin <em>required_plugin_name</em> is not installed or activated. Some features may not work properly.</p>
  </div>
  <?php
}