OAuth, or Open Authorization, is a standard protocol for secure and delegated access. It is crucial in social media integration as it allows third-party applications to access user data without exposing login credentials. Understanding OAuth enhances the security and user experience of social media logins in CodeIgniter.

If 'auto-connect' is set to false, the $this->db->initialize() function is used in CodeIgniter to manually connect to the database.

In CodeIgniter, Models can be utilized to implement data validation rules by incorporating validation logic within Model methods. The $this->form_validation library is typically used in Controllers for form validation, but within Models, developers have the flexibility to define custom validation rules and logic tailored to the data layer. This approach helps maintain separation of concerns and ensures that data validation is an integral part of the overall application architecture.

The Unit Testing Library is commonly used in CodeIgniter for unit testing. It provides functions to perform various types of tests, such as checking if two values are equal or validating the existence of a specific item. This library facilitates the creation and execution of unit tests in a CodeIgniter application.

Database Migrations in CodeIgniter play a crucial role in version controlling the database schema. This is particularly beneficial in continuous integration environments, where changes to the database can be tracked, applied, and rolled back systematically, ensuring a consistent and reliable database structure across different environments.

In CodeIgniter 4, the Model's 'find' method enhances data retrieval flexibility by facilitating the retrieval of records based on primary key values. This method simplifies the process of fetching a specific record from the database, providing a convenient and efficient way to retrieve data using the primary key as a reference.

During high traffic, using shared database connections in CodeIgniter is a recommended practice. It helps manage and reuse existing database connections, reducing the impact of opening and closing connections frequently during peak times.

In CodeIgniter, views are typically saved with a .php extension. This allows the server to interpret and process the PHP code within the view file. The .html extension is not commonly used for CodeIgniter views.

HTML encoding helps prevent XSS attacks by converting special characters to their HTML entities, making them harmless.

CodeIgniter's Active Record is a powerful database abstraction class that simplifies and enhances database interactions. Utilizing Active Record can lead to cleaner code, improved security, and better performance compared to raw SQL queries.