Automatically calculate the correct expiration date based on product term for new members.

membership_experation_date_calculator.php

<?php 

/**
 * Membership Expiration Date Calculation
 * 
 * When someone submits Form 7 and picks a 1-, 2-, or 3-year membership option (field 10), this code creates a brand-new
 * membership that starts today and expires exactly that many years in the future, then puts the expiration date into hidden
 * field 16 so it gets saved to the user’s 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_7', function( $form ) {

    // -----------------------------------------------------
    // 1. Get the raw product field value (full label|price)
    // -----------------------------------------------------
    $selected_value = rgpost('input_10');

    if ( ! $selected_value ) {
        return $form; // No membership selected
    }

    // -----------------------------------------------------
    // 2. Determine membership duration (1, 2, or 3 years)
    // -----------------------------------------------------
    $years = 0;

    // Match against the label text
    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 nothing matched, do not populate expiration
    if ( $years === 0 ) {
        return $form;
    }

    // -----------------------------------------------------
    // 3. Calculate expiration date
    // -----------------------------------------------------
    $start = new DateTime();                    // today's date
    $start->modify( '+' . $years . ' year' );   // add membership period
    $expiration_date = $start->format('m/d/Y'); // save format: MM/DD/YYYY

    // -----------------------------------------------------
    // 4. Store the expiration date in hidden field 16
    // -----------------------------------------------------
    $_POST['input_16'] = $expiration_date;

    return $form;
});