In CodeIgniter, the load function with an array parameter is used to load multiple Helpers at once. You can pass an array of Helper names, and CodeIgniter will load all of them, making it convenient when you need to use multiple Helpers in a controller or model.

To safeguard against XSS attacks while allowing some HTML content, a developer should use output escaping. This technique ensures that any user-supplied data displayed in the application is properly encoded, preventing malicious scripts from being executed. Output escaping is a defensive coding practice to enhance security.

API (Application Programming Interface) is a set of rules that allows one software application to interact with another. In the context of social media integration, it enables communication between the web application and social media platforms.

In the case of a 'database connection error' in a deployed CodeIgniter application, the immediate step is to check the database connection configuration. This involves verifying the database hostname, username, password, and database name in the database.php configuration file to ensure they match the production environment.

When image files are executed as scripts, it suggests a lack of proper input validation, allowing malicious content to be processed. Input validation ensures that the uploaded files are of the expected type and do not contain harmful code.

The correct global array to define database connection parameters in CodeIgniter is $config['database']. This array holds values such as 'hostname', 'username', 'password', 'database', etc.

Fine-tuning caching mechanisms, such as optimizing query caching and view caching, is crucial for advanced CodeIgniter performance optimization. It helps reduce the load on the server and speeds up application response times.

The last_query() function in CodeIgniter's database helper is used for debugging by displaying the last executed database query. It helps developers inspect and troubleshoot database interactions during development.

Pre-submission validation checks data against a set of rules before it's submitted, ensuring that only valid data is processed, enhancing the integrity of the submitted information.

Using a whitelist approach for input validation in SQL injection defense involves allowing only predefined, safe inputs to be accepted by the application. This approach helps prevent SQL injection by explicitly specifying the permissible inputs, thereby reducing the risk of unauthorized SQL commands being injected into the application.

To ensure backward compatibility, unit testing should prioritize handling deprecated functions. This ensures that the existing functionalities remain intact even with the updates.

The primary purpose of logging in CodeIgniter is to track errors and issues within the application. It helps developers identify and fix problems, leading to a more robust and stable application.