Añadir campo cif en el registro de wordpress

//Añadir campo cif registro usuario

//FRONTEND

	//Displaying the field

	add_action( 'register_form', 'crf_registration_form' );
	function crf_registration_form() {

		$cif = ! empty( $_POST['cif'] ) ? intval( $_POST['cif'] ) : '';

		?>
		<p>
			<label for="cif"><?php esc_html_e( 'CIF', 'crf' ) ?><br/>
				<input type="text"
					id="cif"
					name="cif"
					value="<?php echo esc_attr( $cif ); ?>"
					class="input"
					required
				/>
			</label>
		</p>
        <style>
            #cif.fallo{
                border-color: red;
            }

            label[for="cif"]::after{
                color: red;
            }

            label[for="cif"].vacio::after{
                content: 'Por favor introduce el CIF.';
            }

            label[for="cif"].caracteres::after{
                content: 'El CIF debe contener 9 caracteres.';
            }
        </style>
        <script>
            function validar(){
                var cif = jQuery('#cif');
                var ciflabel = jQuery('label[for="cif"]');
                if(cif.val() == ''){
                    cif.addClass('fallo');
                    ciflabel.removeClass('caracteres');
                    ciflabel.addClass('vacio');
                    return false;
                }else if(cif.val().length > 9 || cif.val().length < 9){
                        cif.addClass('vacio');
                        ciflabel.removeClass('vacio');
                        ciflabel.addClass('caracteres');
                        return false;
                }
            }
            jQuery('#registerform').attr('onsubmit','return validar()');
        </script>
		<?php
	}

	//Validating the field

	/*add_filter( 'registration_errors', 'crf_registration_errors', 10, 3 );
	function crf_registration_errors( $errors, $sanitized_user_login, $user_email ) {

		if ( empty( $_POST['cif'] ) ) {
			$errors->add( 'cif_error', __( '<strong>Error</strong>: Por favor introduce el CIF.', 'crf' ) );
		}

		if(strlen($_POST['cif']) > 9 || strlen($_POST['cif']) < 9){
			$errors->add( 'cif_error', __( '<strong>Error</strong>: El CIF debe contener 9 caracteres.', 'crf' ) );
		}

		return $errors;
	}*/

	//Sanitizing and saving the field

	add_action( 'user_register', 'crf_user_register' );
	function crf_user_register( $user_id ) {
		if ( ! empty( $_POST['cif'] ) ) {
			update_user_meta( $user_id, 'cif', intval( $_POST['cif'] ) );
		}
	}

//BACKEND

	//Displaying the field

	add_action( 'user_new_form', 'crf_admin_registration_form' );
	function crf_admin_registration_form( $operation ) {
		if ( 'add-new-user' !== $operation ) {
			// $operation may also be 'add-existing-user'
			return;
		}

		$cif = ! empty( $_POST['cif'] ) ? intval( $_POST['cif'] ) : '';

		?>
		<h3><?php esc_html_e( 'Información personal', 'crf' ); ?></h3>

		<table class="form-table">
			<tr>
				<th><label for="cif"><?php esc_html_e( 'CIF', 'crf' ); ?></label> <span class="description"><?php esc_html_e( '(required)', 'crf' ); ?></span></th>
				<td>
					<input type="text"
					id="cif"
					name="cif"
					value="<?php echo esc_attr( $cif ); ?>"
					class="regular-text"
					required
					/>
				</td>
			</tr>
		</table>
		<?php
	}

	//Validating the field

	add_action( 'user_profile_update_errors', 'crf_user_profile_update_errors', 10, 3 );
	function crf_user_profile_update_errors( $errors, $update, $user ) {
		if ( $update ) {
			return;
		}

		if ( empty( $_POST['cif'] ) ) {
			$errors->add( 'cif_error', __( '<strong>Error</strong>: Por favor introduce el CIF.', 'crf' ) );
		}

		if(strlen($_POST['cif']) > 9 || strlen($_POST['cif']) < 9){
			$errors->add( 'cif_error', __( '<strong>Error</strong>: El CIF debe contener 9 caracteres.', 'crf' ) );
		}

	}

	//Sanitizing and saving the field

	add_action( 'edit_user_created_user', 'crf_user_register' );

	//Profile display

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

	function crf_show_extra_profile_fields( $user ) {
		?>
		<h3><?php esc_html_e( 'Información personal', 'crf' ); ?></h3>

		<table class="form-table">
			<tr>
				<th><label for="cif"><?php esc_html_e( 'CIF', 'crf' ); ?></label></th>
				<td><?php echo esc_html( get_the_author_meta( 'cif', $user->ID ) ); ?></td>
			</tr>
		</table>
		<?php
	}