Stop members downgrading their membership level

[dwanjuki]

This snippet can be used to prevent members from downgrading their levels on sites with hierarchical memberships.

Originally a "make your day" snippet for a customer.

Not MMPU-compatible.

[flintfromthebasement]

PR: #280 — Stop members downgrading their membership level
dwanjuki → dev | 1 file, +67 -0 lines
#280

Summary
Clean, well-structured snippet with good early-returns and readable logic. One unchecked return value will cause a PHP fatal in edge cases; fix that and this is ready to merge.

Issues

• Major stop-members-from-downgrading-level.php:39-40 — pmpro_getLevelAtCheckout() can return null (bare return;) when no valid level ID is found. The snippet immediately dereferences $checkout_level->id without a null check, which throws a fatal PHP error in PHP 8+ and a fatal "Call to a member function on null" in older versions — crashing checkout for any user who hits that path.

  Confirmed in core: pmpro_getLevelAtCheckout() does return; (null) if $level_id is empty or < 1 after all fallbacks exhaust.

  Fix: add a null check immediately after fetching the checkout level:

  $checkout_level = pmpro_getLevelAtCheckout();
  if ( empty( $checkout_level ) ) {
      return $okay;
  }
  $checkout_level_id = $checkout_level->id;

• Minor stop-members-from-downgrading-level.php:10 — link: TBD is a placeholder. Needs a real URL before this goes live, or at minimum a tracking note that it needs updating at publish time.

• Minor stop-members-from-downgrading-level.php:51-52 — array_search() is called without the $strict third argument. The $level_order array holds integers and the IDs come from ->id (also integers), so type coercion isn't currently a problem — but the false-for-not-found check on line 53 relies on strict comparison (false ===), which is inconsistent with a non-strict search. Use array_search( $checkout_level_id, $level_order, true ) to make the intent explicit and guard against any future type drift.

Looks Good

• The false === $member_level check at line 33 and the $checkout_level_rank || $member_level_rank bail at line 53 both use strict comparison correctly — avoids the classic array_search returning 0 (falsy but not false) problem.
• Renewal short-circuit at line 43 is correct and necessary.
• The MMPU incompatibility is clearly documented in both the PR description and the file header.