Apply Canadian taxes to Checkouts with PMPro

my_pmpro_canadian_tax.php

<?php
/*
 * Plugin Name: Paid Memberships Pro - Canadian Tax
 * Description: Apply Canadian taxes to Checkouts with PMPro
 * Version: .1
 * Author: Stranger Studios
 * Author URI: http://www.strangerstudios.com
 */

/*
 * Tax solution for Canada
 * Tax rate charged is based on the user's state.
 *
 * This solution is based off of tax rates in January 2020
 * More info: https://canadabusiness.ca/government/taxes-gst-hst/federal-tax-information/overview-of-charging-and-collecting-sales-tax/
 *
 * Edit as needed, then save this file in your plugins folder and activate it through the plugins page in the WP dashboard.
 */

/**
 * If Canadian resident, set tax based on selected state.
 */
function my_pmpro_canadian_tax( $tax, $values, $order ) {
	$tax_state = '';

	if ( isset( $_REQUEST['canadian_tax_state'] ) ) {
		$tax_state = $_REQUEST['canadian_tax_state'];
	} elseif ( isset( $_SESSION['canadian_tax_state'] ) ) {
		$tax_state = $_SESSION['canadian_tax_state'];
	}

	$canadian_tax_rates = array(
		'AB' => 0.05,
		'BC' => 0.12,
		'MB' => 0.12,
		'NB' => 0.15,
		'NL' => 0.15,
		'NS' => 0.15,
		'NT' => 0.05,
		'NU' => 0.05,
		'ON' => 0.13,
		'PE' => 0.15,
		'QC' => 0.14975,
		'SK' => 0.11,
		'YT' => 0.05,
	);

	if ( isset( $canadian_tax_rates[ $tax_state ] ) ) {
		$tax = round( (float) $values[ price ] * $canadian_tax_rates[ $tax_state ], 2 );
	}
	return $tax;
}

/**
 * Edit level cost text to make users aware of tax for Canadian residents.
 */
function my_pmpro_canadian_tax_level_cost_text( $cost, $level ) {
	$cost .= __(' Customers in Canada will be charged tax based on their state.', 'pmpro-canadian-tax');

	return $cost;
}
add_filter( 'pmpro_level_cost_text', 'my_pmpro_canadian_tax_level_cost_text', 10, 2 );

/**
 * Set the default country for billing to Canada.
 */
function my_pmpro_canadian_tax_default_country( $country ) {
	return 'CA';
}
add_filter( 'pmpro_default_country', 'my_pmpro_canadian_tax_default_country' );

/**
 * Add checkbox and dropdown for users to declare themselves as Canadian
 * residents and choose their state.
 */
function my_pmpro_canadian_tax_checkout_boxes() {
	?>
<table id="pmpro_pricing_fields" class="pmpro_checkout" width="100%" cellpadding="0" cellspacing="0" border="0">
<thead>
	<tr>
		<th>
			<?php esc_html_e( 'Canadian Residents', 'pmpro-canadian-tax' ); ?>
		</th>						
	</tr>
</thead>
<tbody>                
	<tr>	
		<td>
			<div>				
				<input id="user_in_canadian_taxregion" name="user_in_canadian_taxregion" type="checkbox" value="1" onchange="my_pmpro_canadian_taxes_checkbox_changed()" <?php if ( ! empty( $_REQUEST['user_in_canadian_taxregion'] ) || ! empty( $_SESSION['user_in_canadian_taxregion'] ) ) { ?>checked="checked"<?php } ?> /> <label for="user_in_canadian_taxregion" class="pmpro_normal pmpro_clickable"><?php _e('Check this box if your billing address is in Canada.', 'pmpro-canadian-tax');?></label>
			</div>				
		</td>
	</tr>
	<tr id="my_pmpro_canadian_tax_state_select_tr" <?php if( empty( $_REQUEST['user_in_canadian_taxregion'] ) && empty( $_SESSION['user_in_canadian_taxregion'] ) ) {?>hidden<?php } ?> >
		<td>
			<div>
				<label for="canadian_tax_state"><?php esc_html_e( 'Select your state.', 'pmpro-canadian-tax' ); ?></label>
				<select id="canadian_tax_state" name="canadian_tax_state">
					<?php
					$canadian_states = array(
						'AB' => 'Alberta',
						'BC' => 'British Columbia',
						'MB' => 'Manitoba',
						'NB' => 'New Brunswick',
						'NL' => 'Newfoundland & Labrador',
						'NS' => 'Nova Scotia',
						'NT' => 'Northwest Territories',
						'NU' => 'Nunavut',
						'ON' => 'Ontario',
						'PE' => 'Prince Edward Island',
						'QC' => 'Quebec',
						'SK' => 'Saskatchewan',
						'YT' => 'Yukon',
					);
					foreach ( $canadian_states as $state_code => $state_name ) {
						$selected = '';
						if (
							( isset( $_REQUEST['canadian_tax_state'] ) && $_REQUEST['canadian_tax_state'] === $state_code ) ||
							( isset( $_SESSION['canadian_tax_state'] ) && $_SESSION['canadian_tax_state'] === $state_code )
						) {
							$selected = ' selected';
						}
						echo '<option value="' . $state_code . '"' . $selected . '>' . $state_name . '</option>';
					}
					?>
				</select>
			</div>				
		</td>
	</tr>
</tbody>
</table>
<script>
	function my_pmpro_canadian_taxes_checkbox_changed()
	{
		if(jQuery('#user_in_canadian_taxregion').is(":checked"))   
			jQuery("#my_pmpro_canadian_tax_state_select_tr").show();
		else
			jQuery("#my_pmpro_canadian_tax_state_select_tr").hide();
	}
</script>
	<?php
}
add_action( 'pmpro_checkout_boxes', 'my_pmpro_canadian_tax_checkout_boxes' );

/**
 * Check whether user declared themself as Canadian resident.
 */
function my_pmpro_canadian_tax_check() {
	// Check request and session.
	if ( isset( $_REQUEST['user_in_canadian_taxregion'] ) ) {
		// Not empty? setup the tax function.
		if ( ! empty( $_REQUEST['user_in_canadian_taxregion'] ) ) {
			add_filter( 'pmpro_tax', 'my_pmpro_canadian_tax', 10, 3 );
		}
	} elseif ( ! empty( $_SESSION['user_in_canadian_taxregion'] ) ) {
		// Add the filter.
		add_filter( 'pmpro_tax', 'my_pmpro_canadian_tax', 10, 3 );
	}
}
add_action( 'init', 'my_pmpro_canadian_tax_check', 22 );

/**
 * Save Canadian residence info into $_SESSION for off-site checkouts
 */
function my_pmpro_canadian_tax_session_vars() {
	if ( isset( $_REQUEST['user_in_canadian_taxregion'] ) && isset( $_REQUEST['canadian_tax_state'] ) ) {
		$_SESSION['user_in_canadian_taxregion'] = $_REQUEST['user_in_canadian_taxregion'];
		$_SESSION['canadian_tax_state']         = $_REQUEST['canadian_tax_state'];
	}
}
add_action( 'pmpro_paypalexpress_session_vars', 'my_pmpro_canadian_tax_session_vars' );
add_action( 'pmpro_before_send_to_twocheckout', 'my_pmpro_canadian_tax_session_vars', 10, 0 );

/**
 * Remove the session variables after checkout is complete.
 */
function my_pmpro_canadian_tax_after_checkout() {
	if ( isset( $_SESSION['user_in_canadian_taxregion'] ) ) {
		unset( $_SESSION['user_in_canadian_taxregion'] );
	}
	if ( isset( $_SESSION['canadian_tax_state'] ) ) {
		unset( $_SESSION['canadian_tax_state'] );
	}
}
add_action( 'pmpro_after_checkout', 'my_pmpro_canadian_tax_after_checkout' );