ninja_tables_json_data_api.php

<?php

/*
 * Code snippet to expose ninja tables data as JSON via URL
 * Example URL: https://yourdomain.com/?get_ninja_table_data=1463&key=your_security_key
 * In this url 1463 is the table ID that you want to access the data using JSON
 * You should change the key 'your_security_key' in the url as well in the code
 * to protect the endpoint 
 */
add_action('init', function() {
   if(isset($_GET['get_ninja_table_data'])) {
       $securityKey = 'your_security_key';
       $key = $_GET['key'];
       if($key != $securityKey) {
           exit('key mismatch');
       }
       $tableId = intval($_GET['get_ninja_table_data']);
       $data = ninjaTablesGetTablesDataByID($tableId);
       wp_send_json($data);
   }
});

Thank you for showing this option - I have modernized this concept to leverage the built in REST api features of WordPress at https://gist.github.com/codearachnid/9a083f2e6dd018f3643df7622437f2a6