Add notice explaining what has happened when the plugin is deactivated

Author: sheabunge

code-snippets.php

@@ -37,6 +37,16 @@
 if ( defined( 'CODE_SNIPPETS_FILE' ) ) {
 	require_once ABSPATH . 'wp-admin/includes/plugin.php';
 	deactivate_plugins( array( 'code-snippets/code-snippets.php' ), true );
+
+	if ( ! function_exists( 'code_snippets_deactivated_old_version_notice' ) ) {
+		function code_snippets_deactivated_old_version_notice() {
+			echo '<div class="error fade"><p>',
+			esc_html__( 'Another version of Code Snippets appears to be installed. Deactivating this version.', 'code-snippets' ),
+			'</p></div>';
+		}
+	}
+
+	add_action( 'admin_notices', 'code_snippets_deactivated_old_version_notice', 11 );
 	return;
 }