Automatically calculate the correct new expiration date based on product term and current membership term and status

membership_renewal_calculation.php

<?php 

/**
 * Membership Renewal Calculation
 * 
 * When a logged-in user submits the membership renewal form (ID 1), automatically calculate the correct new expiration date,
 * extending from their current expiration if active, or from today if expired, based on whether they chose a 1, 2, or 3-year
 * renewal, and save it to their user profile.
 *
 * Usage: Change the form and field ID numbers to match those used in your form.
 * 
 * Author: Chris Eggleston
 * Version: 1.0
 * 
 *
 */

add_action( 'gform_pre_submission_1', function( $form ) {

    // -----------------------------------------------------
    // 1. Get the selected renewal product option
    // -----------------------------------------------------
    $selected_value = rgpost('input_10');
    if ( ! $selected_value ) {
        return $form;
    }

    // -----------------------------------------------------
    // 2. Determine membership duration (1, 2, 3 years)
    // -----------------------------------------------------
    $years = 0;
    if ( stripos( $selected_value, '1 Year' ) !== false ) {
        $years = 1;
    } elseif ( stripos( $selected_value, '2 Years' ) !== false ) {
        $years = 2;
    } elseif ( stripos( $selected_value, '3 Years' ) !== false ) {
        $years = 3;
    }
    if ( $years === 0 ) {
        return $form;
    }

    // -----------------------------------------------------
    // 3. Get current expiration from user meta
    // -----------------------------------------------------
    $user_id = get_current_user_id();
    $current_expiration = get_user_meta( $user_id, 'membership_expiration', true );

    $today = new DateTime();
    $base_date = null;

    // -----------------------------------------------------
    // 4. Determine the starting point for the renewal
    // -----------------------------------------------------
    if ( $current_expiration ) {

        try {
            $expiration_dt = DateTime::createFromFormat( 'm/d/Y', $current_expiration );

            if ( $expiration_dt && $expiration_dt >= $today ) {
                // ACTIVE MEMBERSHIP — extend from expiration date
                $base_date = $expiration_dt;
            } else {
                // EXPIRED — renew from today
                $base_date = $today;
            }

        } catch ( Exception $e ) {
            // If corrupted value, renew from today
            $base_date = $today;
        }

    } else {
        // No previous expiration found — new membership or data missing
        $base_date = $today;
    }

    // -----------------------------------------------------
    // 5. Apply membership extension
    // -----------------------------------------------------
    $base_date->modify( '+' . $years . ' year' );
    $new_expiration = $base_date->format('m/d/Y');

    // -----------------------------------------------------
    // 6. Store in hidden expiration field 16
    //    User Registration Add-on will save to usermeta
    // -----------------------------------------------------
    $_POST['input_16'] = $new_expiration;

    return $form;
});