Allows customers to select membership duration at checkout. Adjusts the amount charged and expiration date of the membership accordingly.

pmpro-select-membership-duration.php

<?php
/**
 * Allow customers to select membership duration at checkout. Adjust the amount charged and expiration date of the membership accordingly.
 *
 * Add this code below to your PMPro Customizations Plugin - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 *
 * Requires the Paid Memberships Pro Register Helper Add On to be installed and activated in order to work:
 * https://www.paidmembershipspro.com/add-ons/pmpro-register-helper-add-checkout-and-profile-fields/
 */

/**
 * Instantiate the Register Helper class
 *
 * @return [type] [description]
 */
function my_pmprorh_init() {

    // don't break if Register Helper is not loaded
    if ( ! function_exists( 'pmprorh_add_registration_field' ) ) {
        return false;
    }

    // define the fields
    $fields = array();
    $fields[] = new PMProRH_Field(
        'membership_duration',
        'select',
        array(
            'label'     => 'Membership Duration',
            'options'    => array(
                'no' => '1 Year',
                2 => '2 Years',
                3 => '3 Years',
            ),
            'levels' => array( 8 ), // Make sure this is to only show for yearly membership options. Set array number to relevant level ID.
        )
    );
    // add the fields into a new checkout_boxes are of the checkout page
    foreach ( $fields as $field ) {
        pmprorh_add_registration_field(
            'checkout_boxes',
            $field
        );
    }

}
add_action( 'init', 'my_pmprorh_init' );

/**
 * my_pmpro_checkout_level Alters the amount charged and the expiration date of the membership depending on duration selected by user.
 *
 * @param  object $level The $pmpro_level object prior to duration being added.
 *
 * @return object $level The callback function returns the modified $pmpro_level object with the added duration.
 */
function my_pmpro_checkout_level( $level ) {

    $duration = isset( $_REQUEST['membership_duration'] ) ? $_REQUEST['membership_duration'] : '';

    // Bail if no duration is set.
    if ( empty( $duration ) ) {
        return $level;
    }

    // Bail if the user hasn't selected a duration and keep level intact.
    if ( 'no' === $duration ) {
        return $level;
    }

    // Duration for 2 years, give 20% discount.
    if ( '2' === $duration ) {
            $duration = 2;
            $discount_percentage = 0.2;
    }

    // Duration for 3 years, give 25% discount.
    if ( '3' === $duration ) {
        $duration = 3;
        $discount_percentage = 0.25;
    }

    /**
     * Set the duration to selected and adjust the charged amount.
     *
     * Please Note - the new amount will only show upon redirecting to payment gateway page.
     */
    if ( is_int( $duration ) ) {

        // Set the level's duration.
        $level->expiration_number = $duration;
        $level->expiration_period = 'Year';

        // Let's calculate the new price with discount.
        $new_amount = $duration * $level->initial_payment;
        $discount_amount = $new_amount * $discount_percentage;

        // Set the level's new price.
        $level->initial_payment = round( $new_amount - $discount_amount );
    }

    return $level;
}
add_filter( 'pmpro_checkout_level', 'my_pmpro_checkout_level' );

There seems to be some issues with renewing members. Specifically, with setting the expiration date. It doesn't add the original days remaining to the renewal purchase.

There might also be issues with PayPal checkout.

Both of these seem to originate from the previous code snippet done by me :-(

This recipe is included in the blog post on "Add a Membership Duration dropdown to Checkout and Offer a Discount for Extending Membership" at Paid Memberships Pro here: https://www.paidmembershipspro.com/add-a-membership-duration-dropdown-to-checkout-and-offer-a-discount-for-extending-membership/