Get the term IDs associated with the choosen membership levels assigned to a post or page. Only returns taxonomy terms.

wc-membership-object-ids-by-post.php

<?php
/**
 * Get the page/post IDs or taxonomy term IDs for restricted content 
 * for chosen WooCommerce Memberships levels which have been assigned to a post or page.
 *
 * @param  string $content_type | accepts either 'taxonomy' or 'post_type' object keys
 * @param  int    $post_id The ID of the post or page
 * @return array  post/pageID's or taxonomy term ID's
 */
function wc_get_membership_term_ids( $content_type, $post_id ) {
	// check if woomembership plugin function exists
	if ( ! function_exists( 'wc_memberships_get_membership_plan' ) ) {
		return;
	}

	// Get the rules set in each page / post
	$rules = wc_memberships()->rules->get_post_content_restriction_rules( $post_id );

	// If no rules are set on the page/post return early
	if ( empty( $rules ) ) {
		return;
	}

	// set variables as empty arrays
	$access = $object_ids = array();

	// For each rule add the available object id's to the object_ids array
	foreach ( $rules as $rule ) {

		// get the membership plan object
		$membership_plan = wc_memberships_get_membership_plan( $rule->get_membership_plan_id() );

		// check whether the current user has access to the membership plan
		$access = wc_memberships_is_user_active_member( get_current_user_id(), $membership_plan );

		// if the user has access assign the ID to the object ID array
		// or if the user is the admin
		if ( $access || current_user_can( 'manage_options' ) ) {

			// if content restriction rules are set get the rules per membership plan
			$content_restriction_rules = isset( $membership_plan ) ? $membership_plan->get_content_restriction_rules() : array();

			foreach ( $content_restriction_rules as $restriction_rule ) {
				// get the object IDs associated with the restriction rules
				if ( is_object( $restriction_rule ) && $content_type === $restriction_rule->get_content_type() ) {

					foreach ( $restriction_rule->get_object_ids() as $id ) {
						$object_ids[] = $id;
					}

				}
			}
		}
	}
	// returns an array of content type IDs
	return $object_ids;
}