Checks if a user is logged in, if not it redirects them to the login page.

Retrieve info for user lists to prevent multiple queries by get_userdata()

Ensures intent by verifying that a user was referred from another admin page with the correct security nonce.

Verifies the Ajax request to prevent processing requests external of the blog.

Retrieve the avatar <img> tag for a user, email address, MD5 hash, comment, or post.

Retrieve user info by a given field

Retrieve user info by user ID.

Determines whether the current visitor is a logged in user.

Authenticate a user, confirming the login credentials are valid.

Checks the plaintext password against the encrypted Password.