get_the_author_meta()

function get_the_author_meta( $field = '', $user_id = false ) {
	$original_user_id = $user_id;

	if ( ! $user_id ) {
		global $authordata;
		$user_id = isset( $authordata->ID ) ? $authordata->ID : 0;
	} else {
		$authordata = get_userdata( $user_id );
	}

	if ( in_array( $field, array( 'login', 'pass', 'nicename', 'email', 'url', 'registered', 'activation_key', 'status' ), true ) ) {
		$field = 'user_' . $field;
	}

	$value = isset( $authordata->$field ) ? $authordata->$field : '';

	/**
	 * Filters the value of the requested user metadata.
	 *
	 * The filter name is dynamic and depends on the $field parameter of the function.
	 *
	 * @since 2.8.0
	 * @since 4.3.0 The `$original_user_id` parameter was added.
	 *
	 * @param string    $value            The value of the metadata.
	 * @param int       $user_id          The user ID for the value.
	 * @param int|false $original_user_id The original user ID, as passed to the function.
	 */
	return apply_filters( "get_the_author_{$field}", $value, $user_id, $original_user_id );
}