gistfile1.php

<?php

function my_admin_notices() {
	$success = true;
	if( $success ) {
		?>
		<div class="updated">
			<p><?php _e( '<strong>SUCCESS</strong> Success!', 'mytextdomain' ); ?></p>
		</div>
		<?php
	} else {
		?>
		<div class="error">
			<p><?php _e( '<strong>ERROR</strong> Error!', 'mytextdomain' ); ?></p>
		</div>
		<?php
	}
}

add_action( 'admin_notices', 'my_admin_notices' );