EDD Prevent Double Purchase

functions.php

<?php

// EDD Prevent Double Purchase
function pw_edd_prevent_double_purchase( $valid_data, $post_data ) {
	$cart_items = edd_get_cart_contents();
	foreach( $cart_items as $item ) {
		if( edd_has_user_purchased(  get_current_user_id(), $item['id'] ) ) {
			edd_set_error( 'double_purchase', __( 'You may not purchase this item again until your subscription expires', 'edd' ) );
		}
	}
}
add_action( 'edd_checkout_error_checks', 'pw_edd_prevent_double_purchase', 10, 2 );