WPInvoice notification code (unfinished)

WPInvoice notification code

<?php
function reminder_invoice_notification($wpi_settings) {
    global $wpi_settings;

    // Output the invoice selection field in the settings
    $rinotify .= '<table><tr><th>Select Invoice Template to use:</th><td>';
    $rinotify .= '<select id="wpi_change_notification">';

    foreach ($wpi_settings['notification'] as $key => $item) {
	$rinotify .= "<option value=\"$key\">{$item['name']}</option>"; 
    }
		  
    $rinotify .= '</select>';
    $rinotify .= '</td></tr></table>';
    echo $rinotify;
}

// If the event function is not being called, schedule it to be called
function post_date_activation() {
    if (!wp_next_scheduled( 'post_date_hook' )) {
	wp_schedule_event( time(), 'twicedaily', 'post_date_hook' );
    }
}
add_action('wp', 'post_date_activation');

// Send e-mails to unfulfilled invoices (should be called twice daily)
function post_date_function() {
    global $wpdb, $wpi_settings;

    // This is a timestamp from one week ago... anything that has a last
    //   notified timestamp lower than this needs a new e-mail sent
    $needsNotification = strtotime('-1 week');

    $dbResults = $wpdb->get_results($wpdb->prepare("SELECT post_date FROM {$wpdb->posts} WHERE post_type = 'wpi_object' AND post_status = 'active'"));

    // Check the timestamp on each invoice to see if they need a new
    //   notification e-mail
    foreach ($dbResults as $result) {
	if (strtotime($result->post_modified) < $needsNotification) {
	    // Send e-mail to the customer
	    // TODO: Look at wpi_ajax.php for code to load the notification template from the $wpi_settings variable
	    $invoiceID = wpi_post_id_to_invoice_id($result->ID);
	    $invoice = new WPI_Invoice();
	    $invoice->load_invoice("id=$invoiceID");

	    $name = stripslashes($wpi_settings['business_name']);
	    $from = stripslashes($wpi_settings['email_address']);

	    $permalink = get_invoice_permalink($invoice['invoice_id']);

	    $headers = "From: {$name} <{$from}>\r\n";

	    $message = "Dear {$invoice['user_data']['display_name']},
{$wpi_settings['business_name']} has received your payment for the invoice.

You can overview invoice status and payment history by clicking this link:
{$permalink}

Thank you very much for your patronage.

Best regards,
$name ($from)";

	    $subject = "Invoice #{$invoice['invoice_id']} has been paid";

	    $message = html_entity_decode($message, ENT_QUOTES, 'UTF-8');
	    $subject = html_entity_decode($subject, ENT_QUOTES, 'UTF-8');

	    if (wp_mail($invoice['user_data']['user_email'], $subject, $message, $headers)) {
		WPI_Functions::log_event($result->ID, 'invoice', 'emailed', '', 'Reminder eMailed');
	    }

	    // And update the database notification timestamp with
	    //   the current time
	    // TODO: add code to update the database with last time sent
	}
    }
}

// Call 'post_date_function' when the 'post_date_hook' hook is called
add_action('post_date_hook', 'post_date_function');