Configure one or more membership level(s) as "single-use" trial memberships (i.e. prevent the user from signing up more than once)

pmpro-single-use-trial.php

<?php
/*
Plugin Name: PMPro Single Use Trial Memberships
Plugin URI: http://www.paidmembershipspro.com/wp/pmpro-customizations/
Description: Allow a member to sign up for the trial membership level once
Version: .1
Author: Thomas Sjolshagen @ Stranger Studios <[email protected]>
Author URI: http://www.eighty20results.com/thomas-sjolshagen/
*/

/*
	Only allow users to use the trial level once.

	By default, this add-on cam treat all free membership levels as single-use trial membership
	(re-add the 'add_filter("pmprosut_set_trial_level_id", "pmprosut_set_trial_levels", 1, 1);' line below)
	You'll need to have an expiration date configured for the trial level(s).

	NOTE: Use a filter ('pmprosut_set_trial_level_id') to add/remove level IDs from the list of trial levels
*/

/**
 * Filter to return all free levels as "single-use trial membership levels"
 *
 * @param   array     $level_array    Array of level IDs (one or more).
 * @return  array                     Array of level ID(s).
 */
function pmprosut_set_trial_levels( $level_array ) {

	if (function_exists('pmpro_isLevelFree')) {

		$all_levels = pmpro_getAllLevels(true, true);

		// Add all free levels (trials?) to the filter array
		foreach($all_levels as $level_id => $level ) {

			if ( pmpro_isLevelFree($level)) {
				$level_array[]= $level_id;
			}
		}
	}

	return $level_array;
}
// add_filter('pmprosut_set_trial_level_id', 'pmprosut_set_trial_levels', 1, 1);

/**
 * Return a trial membership level to grant single-usage to.
 * TODO: Replace 50 with the ID of the membership level you want to use as a single-use Trial Membership
 *
 * @param $level_array
 *
 * @return array
 */
function pmprosut_set_single_trial_level( $level_array ) {

	// Set this to the level ID for your (single) trial membership level
	$level_array[] = 50;

	return $level_array;
}
add_filter('pmprosut_set_trial_level_id', 'pmprosut_set_single_trial_level', 10, 1);

//record when users gain the trial level
function pmprosut_after_change_membership_level($level_id, $user_id)
{
	//trial level(s) to allow single sign-ups
	$trial_levels = apply_filters('pmprosut_set_trial_level_id', array());

	if(in_array($level_id, $trial_levels) )
	{
		//add user meta to record the fact that this user has had this level before
		update_user_meta($user_id, "pmpro_trial_level_{$level_id}_used", true);
	}
}
add_action("pmpro_after_change_membership_level", "pmprosut_after_change_membership_level", 10, 2);

//check at checkout if the user has used the trial level already
function pmprosut_registration_checks($value)
{
	global $current_user;

	// array of trial levels
	$trial_levels = apply_filters('pmprosut_set_trial_level_id', array());
	$level_id = intval($_REQUEST['level']);

	if($current_user->ID && in_array( $level_id, $trial_levels) )
	{
		//check if the current user has already used the trial level
		$already = get_user_meta($current_user->ID, "pmpro_trial_level_{$level_id}_used", true);

		//yup, don't let them checkout
		if($already)
		{
			global $pmpro_msg, $pmpro_msgt;
			$pmpro_msg = "You have already used up your trial membership. Please select a full membership to checkout.";
			$pmpro_msgt = "pmpro_error";

			$value = false;
		}
	}

	return $value;
}
add_filter("pmpro_registration_checks", "pmprosut_registration_checks");

//swap the expiration text if the user has used the trial
function pmprosut_level_expiration_text($text, $level)
{
	global $current_user;

	$level_id = $level->id;
	$trial_levels = apply_filters('pmprosut_set_trial_level_id', array());
	$has_used  = get_user_meta($current_user->ID, "pmpro_trial_level_{$level_id}_used", true);

	if( !empty($current_user->ID) && !empty($has_used) && in_array($level_id, $trial_levels))
	{
		$text = "You have already used up your trial membership. Please select a full membership to checkout.";
	}

	return $text;
}
add_filter("pmpro_level_expiration_text", "pmprosut_level_expiration_text", 10, 2);