WooCommerce 2.1 - Extra fields in WooCommerce registration.

functions.php

<?php
/**
 * Add new register fields for WooCommerce registration.
 *
 * @return string Register fields HTML.
 */
function cs_wc_extra_register_fields() {
	?>
	<p class="form-row form-row-first">
		<label for="reg_billing_first_name"><?php _e( 'Nome', 'textdomain' ); ?> <span class="required">*</span></label>
		<input type="text" class="input-text" name="billing_first_name" id="reg_billing_first_name" value="<?php if ( ! empty( $_POST['billing_first_name'] ) ) esc_attr_e( $_POST['billing_first_name'] ); ?>" />
	</p>
	<p class="form-row form-row-last">
		<label for="reg_billing_last_name"><?php _e( 'Sobrenome', 'textdomain' ); ?> <span class="required">*</span></label>
		<input type="text" class="input-text" name="billing_last_name" id="reg_billing_last_name" value="<?php if ( ! empty( $_POST['billing_last_name'] ) ) esc_attr_e( $_POST['billing_last_name'] ); ?>" />
	</p>
	<?php
}

add_action( 'woocommerce_register_form_start', 'cs_wc_extra_register_fields' );

/**
 * Validate the extra register fields.
 *
 * @param  string $username          Current username.
 * @param  string $email             Current email.
 * @param  object $validation_errors WP_Error object.
 *
 * @return void
 */
function cs_wc_validate_extra_register_fields( $username, $email, $validation_errors ) {
	if ( isset( $_POST['billing_first_name'] ) && empty( $_POST['billing_first_name'] ) ) {
		$validation_errors->add( 'billing_first_name_error', __( '<strong>Erro</strong>: Digite o seu nome.', 'textdomain' ) );
	}

	if ( isset( $_POST['billing_last_name'] ) && empty( $_POST['billing_last_name'] ) ) {
		$validation_errors->add( 'billing_last_name_error', __( '<strong>Erro</strong>: Digite o seu sobrenome.', 'textdomain' ) );
	}
}

add_action( 'woocommerce_register_post', 'cs_wc_validate_extra_register_fields', 10, 3 );

/**
 * Save the extra register fields.
 *
 * @param  int  $customer_id Current customer ID.
 *
 * @return void
 */
function cs_wc_save_extra_register_fields( $customer_id ) {
	if ( isset( $_POST['billing_first_name'] ) ) {
		// WordPress default first name field.
		update_user_meta( $customer_id, 'first_name', sanitize_text_field( $_POST['billing_first_name'] ) );

		// WooCommerce billing first name.
		update_user_meta( $customer_id, 'billing_first_name', sanitize_text_field( $_POST['billing_first_name'] ) );
	}

	if ( isset( $_POST['billing_last_name'] ) ) {
		// WordPress default last name field.
		update_user_meta( $customer_id, 'last_name', sanitize_text_field( $_POST['billing_last_name'] ) );

		// WooCommerce billing last name.
		update_user_meta( $customer_id, 'billing_last_name', sanitize_text_field( $_POST['billing_last_name'] ) );
	}
}

add_action( 'woocommerce_created_customer', 'cs_wc_save_extra_register_fields' );

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