Few Tips to create a custom module

Check module exist

if (\Drupal::moduleHandler()->moduleExists('my_module')) {

    $message = 'Module exist.';

}

else {

    $message = 'Not exists.';

}

 

Get module / Theme install directory

$path = drupal_get_path('module', 'my_module');

Get a file in a custom module

$path = drupal_get_path('module', 'my_module') . '/my_module.info.yml';