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filter is not described

registration_errors filter-hook . WP 2.1.0

Filters the errors encountered when a new user is being registered.

The filtered WP_Error object may, for example, contain errors for an invalid or existing username or email address. A WP_Error object should always returned, but may or may not contain errors.

If any errors are present in $errors, this will abort the user's registration.

Usage

add_filter( 'registration_errors', 'filter_function_name_8468', 10, 3 );
function filter_function_name_8468( $errors, $sanitized_user_login, $user_email ){
	// filter...

	return $errors;
}
$errors(WP_Error)
A WP_Error object containing any errors encountered during registration.
$sanitized_user_login(string)
User's username after it has been sanitized.
$user_email(string)
User's email.

Where the hook is called

register_new_user()
registration_errors
wp-includes/user.php 2411
$errors = apply_filters( 'registration_errors', $errors, $sanitized_user_login, $user_email );

Where the hook is used (in WP core)

Does not used.