add custom user meta fields to profile

functions.php

add_action( 'show_user_profile', 'add_kdnr_field' );
add_action( 'edit_user_profile', 'add_kdnr_field' );

function add_kdnr_field( $user ) { ?>
    <table class="form-table">
    <tr>
        <th><label for="address">Kundennummer</label></th>
        <td>
            <input type="text" name="kdnr" id="kdnr" value="<?php echo esc_attr( get_the_author_meta( 'kdnr', $user->ID ) ); ?>" class="regular-text" /><br />
            <span class="description">Bitte füge deine Kundennummer ein.</span>
        </td>
    </tr>
    </table>
<?php }

add_action( 'personal_options_update', 'save_kdnr_field' );
add_action( 'edit_user_profile_update', 'save_kdnr_field' );

function save_kdnr_field( $user_id ) {
    if ( !current_user_can( 'edit_user', $user_id ) ) { 
        return false; 
    }
    update_user_meta( $user_id, 'kdnr', $_POST['kdnr'] );
}