Allow curly brackets in Ninja Forms notifications.

ninja-forms-allow-curly-brackets-in-notifications.php

<?php
/**
 * Allow text between brackets in Ninja Forms notifications.
 *
 * - How to Use: wrap the text you want to put inside curly brackets in double square brackets, e.g. `[[tag]]`. 
 * - Setup: Add this code to your website (I recommend using the plugin Code Snippets).
 *
 * @author Nabil @ REI Conversion
 */
add_filter( 'ninja_forms_action_email_message',  function($message) {
    $replacements = [
        '[[' => '{',
        ']]' => '}',
    ];
    return str_replace(
        array_keys( $replacements ),
        array_values( $replacements ),
        $message
    );
} );