Offer one-time trials using the Subscription Delays Add On

one_time_trial_delay_pmpro_registration_checks.php

<?php
/**
 * This code stores data when a user checks out for a level. 
 * If that user tries to checkout for the same level, the Subscription Delay is removed. 
 * The user is instead charged for their first subscription payment at checkout.
 *
 */

// Record when users gain the trial level.
function one_time_trial_save_trial_level_used( $level_id, $user_id ) {
	// Set this to the ID of your trial level.
	$trial_level_id = 1; // Membership Level ID

	if ( $level_id == $trial_level_id ) {	
    	// Add user meta to record that the user has received their one-time trial.
		update_user_meta( $user_id, 'pmpro_trial_level_used', $trial_level_id );
	}	
}
add_action( 'pmpro_after_change_membership_level', 'one_time_trial_save_trial_level_used', 10, 2 );

// Show the user's trial meta setting for admins on the Edit Profile page.
function one_time_trial_show_trial_level_used( $user ) { 
	if ( current_user_can( 'edit_users' ) ) { ?>
		<h3>One-Time Trial</h3>
		<table class="form-table"> 
			<tbody>
				<tr>
					<th scope="row"></th>
					<td>
						<?php 
							$already = get_user_meta( $user->ID, 'pmpro_trial_level_used', true );
							if ( ! empty( $already ) && $already == '1' ) {
								echo 'Trial period has been claimed.';
							} else {
								echo 'Trial period not claimed.';
							}
						?>
					</td>
				</tr>
			</tbody>
		</table>
	<?php
	}
}
add_action( 'show_user_profile', 'one_time_trial_show_trial_level_used' );
add_action( 'edit_user_profile', 'one_time_trial_show_trial_level_used' );

// Check if the user has received their one-time trial at checkout.
function one_time_trial_delay_pmpro_registration_checks() {
	global $current_user;

	//set this to the id of your trial level
	$trial_level_id = 1; // Membership Level ID
	if ( ! empty( $_REQUEST['level'] ) ) {
		$checkout_level_id = intval( $_REQUEST['level'] );
	}

	if ( ! empty( $current_user->ID ) && ! empty( $checkout_level_id ) && $checkout_level_id == $trial_level_id ) {
		// Check the current user's meta.
		$already = get_user_meta( $current_user->ID, 'pmpro_trial_level_used', true );

		// Remove the subscription delay from checkout. Charge the subscripton immediately.
		if ( $already ) {
			remove_filter( 'pmpro_profile_start_date', 'pmprosd_pmpro_profile_start_date', 10, 2);
			remove_action( 'pmpro_after_checkout', 'pmprosd_pmpro_after_checkout' );
			remove_filter( 'pmpro_next_payment', 'pmprosd_pmpro_next_payment', 10, 3);
			remove_filter( 'pmpro_level_cost_text', 'pmprosd_level_cost_text', 10, 2);
			remove_action( 'pmpro_save_discount_code_level', 'pmprosd_pmpro_save_discount_code_level', 10, 2);
		}
	}	
}
add_filter( 'init', 'one_time_trial_delay_pmpro_registration_checks' );

// Filter the price on the levels page to remove one-time trial.
function one_time_trial_delay_pmpro_level_cost_text( $cost, $level ) {
	global $current_user, $pmpro_pages;

	// Not logged in?
	if ( empty( $current_user->ID ) ) {
		return $cost;
	}

	// Check the current user's meta.
	$already = get_user_meta( $current_user->ID, 'pmpro_trial_level_used', true );
	
	// If the user already had the trial for this level, make initial payment = billing amount.
	if ( $level->id == $already && is_page( $pmpro_pages[ 'levels' ] ) ) {
		$cost = sprintf( __( '<strong>%1$s per %2$s</strong>.', 'paid-memberships-pro' ), pmpro_formatPrice( $level->billing_amount ), pmpro_translate_billing_period( $level->cycle_period ) );
	}

	return $cost;
}
add_filter( 'pmpro_level_cost_text', 'one_time_trial_delay_pmpro_level_cost_text', 15, 2 );

// Filter the price at checkout to charge the billing ammount immediately.
function one_time_trial_delay_pmpro_checkout_level( $level ) {
	global $current_user, $discount_code, $wpdb;

	// Not logged in?
	if ( empty( $current_user->ID ) ) {
		return $level;
	}

	// Not if using a discount code.
	if ( ! empty( $discount_code ) || ! empty( $_REQUEST[ 'discount_code' ] ) ) {
		return $level;
	}

	// Check the current user's meta.
	$already = get_user_meta( $current_user->ID, 'pmpro_trial_level_used', true );

	// If the user already had the trial for this level, make initial payment = billing amount.
	if ( $level->id == $already ) {
		$level->initial_payment = $level->billing_amount;
	}

	return $level;
}
add_filter( 'pmpro_checkout_level', 'one_time_trial_delay_pmpro_checkout_level', 5 );

This recipe is included in the blog post on "Using Subscription Delays Add On for One-Time, Credit Card Required Trials" at Paid Memberships Pro here: https://www.paidmembershipspro.com/subscription-delay-one-time-credit-card-required-trial/