The unset_userdata() function in the CodeIgniter programming language is used to delete data stored in a user session based on its key name.
The following is a more detailed explanation of the function and its use:

What unset_userdata() does:

• Deletes the data associated with a specific key name from the user session.
• Accepts one argument, which is the key name of the data to be deleted.
• Searches for the key name in the session and deletes the corresponding data value if found.

When to use unset_userdata():

1. Cleaning Flashdata:

• Flashdata is a type of session data that only lasts for one request.
• Once displayed, flashdata needs to be deleted so as not to overload the session.
• unset_userdata() helps clear these temporary messages from the session.

2. Clearing Unused Data:

• If you have saved data using set_userdata() during the application process,
• You can delete it with unset_userdata() when the data is no longer required.
• This helps keep sessions clean and optimize resource usage.

Example:

// Mengasumsikan Anda telah menyetel data sebelumnya dengan 'username' sebagai kuncinya
$this->session->set_userdata('username', 'john_doe');

// Nanti dalam kode Anda, ketika Anda tidak lagi membutuhkan username
$this->session->unset_userdata('username');

Things to note:

• unset_userdata() only works with data stored using set_userdata().
• This function will not affect other session management methods such as PHP’s built-in $_SESSION.
• We recommend deleting unnecessary data from sessions using unset_userdata() to optimize performance and storage usage.
• Keep in mind that CodeIgniter underwent changes in version 3.1 and later.
• While the core functionality remains the same, the way you interact with unset_userdata() may vary slightly depending on the version you are using.
• It is always recommended to refer to the official documentation for your specific version to ensure proper usage.

Conclusion:

By effectively utilizing unset_userdata(), you can keep user sessions clean and efficient in your CodeIgniter applications.