Add a box to choose to auto renew at checkout with PMPro.

pmpro_auto_renew_box.php

<?php
/*
*************** !!
	!! IMPORTANT NOTE: This can more easily be done using the addon maintained here: 
	!! https://github.com/strangerstudios/pmpro-auto-renewal-checkbox
*************** !!
	Allow users to choose to auto renew
	
	1. Edit the global variable below to set the renewal amount (can be the same or less) for each level.
	2. Paste this code into your active theme's functions.php or a custom plugin.
*/
global $pmpro_auto_renewal_amounts;		//level_id => billing_amount
$pmpro_auto_renewal_amounts = array(
		"6"=>"47",
		"17"=>"147",
		"18"=>"147",
		"19"=>"147",
		"20"=>"147"
	);

//draw the box
function pmpro_auto_renew_box()
{
	global $pmpro_auto_renewal_amounts, $pmpro_review, $discount_code;

	//only for certain levels
	$level = intval($_REQUEST['level']);
	if(!isset($pmpro_auto_renewal_amounts[$level]))
		return;

	//not if this is an addon package
	if(!empty($_REQUEST['ap']) || !empty($_SESSION['ap']))
		return;
	
	//not if using a discount code
	if(!empty($discount_code))
		return;

	if(!empty($_REQUEST['autorenew']))
		$autorenew = 1;
	else
		$autorenew = 0;
		
	if(!$pmpro_review)
	{
	?>
	<table id="pmpro_payment_method" class="pmpro_checkout top1em" width="100%" cellpadding="0" cellspacing="0" border="0">
		<thead>
			<tr>
				<th>Would you like to set up automatic renewals?</th>
			</tr>
		</thead>
		<tbody>
			<tr>
				<td>
					<div>
						<input type="checkbox" id="autorenew" name="autorenew" value="1" <?php checked($autorenew, 1);?> />
						<input type="hidden" id="autorenew_present" name="autorenew_present" value="1" />
						<label class="pmpro_normal pmpro_clickable" for="autorenew">
							Yes, renew annually at $<?php echo $pmpro_auto_renewal_amounts[$level];?>/yr.
						</label>
					</div>
				</td>
			</tr>
		</tbody>
	</table>
	<?php
	}
	else
	{
		if(!empty($_SESSION['autorenew']))		
		?>
		<input type="hidden" id="autorenew" name="autorenew" value="<?php $autorenew;?>" />
		<input type="hidden" id="autorenew_present" name="autorenew_present" value="1" />
		<?php
	}
}
add_action('pmpro_checkout_boxes', 'pmpro_auto_renew_box', 15);

//save autorenew to session for PayPal Express
function pmpro_auto_renew_pmpro_paypalexpress_session_vars()
{
	if(!empty($_REQUEST['autorenew']))
		$autorenew = 1;
	else
		$autorenew = 0;
		
	$_SESSION['autorenew'] = $autorenew;
	$_SESSION['autorenew_present'] = 1;		
}
add_action('pmpro_paypalexpress_session_vars', 'pmpro_auto_renew_pmpro_paypalexpress_session_vars');

//update level based on selection
function pmpro_auto_renew_checkout_level($level)
{
	global $pmpro_auto_renewal_amounts, $discount_code;
	
	//only for certain levels
	if(!isset($pmpro_auto_renewal_amounts[$level->id]))
		return $level;
	
	//not if addon package
	if(!empty($_REQUEST['ap']) || !empty($_SESSION['ap']))
		return $level;

	//not if using a discount code
	if(!empty($discount_code))
		return $level;

	if(!empty($_REQUEST['autorenew']))
		$autorenew = 1;
	elseif(isset($_REQUEST['autorenew_present']))
		$autorenew = 0;
	elseif(isset($_SESSION['autorenew_present']))
		$autorenew = intval($_SESSION['autorenew']);
	else
		$autorenew = 0;		
		
	if($autorenew)
	{
		$level->billing_amount = $pmpro_auto_renewal_amounts[$level->id];
		$level->cycle_number = 1;
		$level->cycle_period = "Year";
		$level->expiration_number = 0;
	}
	else
	{
		$level->billing_amount = 0;
		$level->cycle_number = 0;
		$level->expiration_number = 1;
		$level->cycle_period = "Year";
	}
		
	return $level;
}
add_filter("pmpro_checkout_level", "pmpro_auto_renew_checkout_level", 7);