See if a commenter has purchased a given download ID

edd-ck-commenter-has-purchased.php

<?php
/*
 * Plugin Name: Easy Digital Downloads - Commenter has purchased
 * Description: Adds a 'Purchased' tag after a commenter who's purchased a download
 * Author: Chris Klosowski
 * Version: 1.0
 */

/**
 * NOTE: This is currently not very performant. If an email address has a lot
 * of purchases, this will take some time to crunch. It should be used sparingly.
 */

/*
 * If the commenter has purchased the product being referenced, return true
 */
function ck_edd_commenter_has_purcahsed( $commenter_email, $download_id ) {

	$customer    = EDD()->customers->get_by( 'email', $commenter_email );
	$payment_ids = explode( ',', $customer->payment_ids );

	// Setup an array to capture all the downloads this email address has purchased
	$purchased_download_ids = array();

	foreach ( $payment_ids as $payment_id ) {

		$payment_downloads  = edd_get_payment_meta_downloads( $payment_id );

		if ( ! is_array( $payment_downloads ) ) {
			continue; // May not be an array due to some very old payments, move along
		}

		foreach ( $payment_downloads as $download ) {
			$purchased_download_ids[] = $download['id'];
		}

	}

	$unique_downloads = array_unique( $purchased_download_ids );

	return in_array( $download_id, $unique_downloads );

}