Snippet to add customer WooCommerce Membership plan as body class

customer-membership-class.php

<?php

add_filter( 'body_class', 'membership_body_class' );
function membership_body_class( $classes ) {
	if ( ! function_exists( 'wc_memberships' ) ) {
		return $classes;
	}

	$user_id = get_current_user_id();
	$args = array( 
		'status' => array( 'active', 'pending-cancellation' ), // Add or remove other statuses if you want
	);
	
	// Get user memberships
	$active_memberships = wc_memberships_get_user_memberships( $user_id, $args );	
	$membershipPlansArray = array();

	if ( ! empty( $active_memberships ) ) {
		// Get user membership plans
		foreach( $active_memberships as $membership ) {
			$membershipPlansArray[] = $membership->plan;
		}
		
		// Get slug for each membership plan and add as class
		foreach( $membershipPlansArray as $membershipPlan ) {
			$classes[] = $membershipPlan->slug;
		}
	}

	return $classes;
}

?>