WPResidence Translate — Performance & Caching (Developer Reference)

This article maps the cache layers inside the WPResidence Translate plugin (wpestate-translate, text domain wpr-translate) so you can reason about invalidation, extend it safely from a child theme or companion plugin, and keep a multi-language real estate website fast at scale.

Cache Layers Overview

Layer	Scope	API	Where
Request-scoped static	Single PHP request	static $cache arrays in functions	includes/translation-runtime.php
Object cache	Persistent if drop-in installed	wp_cache_get() / wp_cache_set() in group wpr_translate	includes/custom-fields-sync.php
Transients (per language)	Cross-request, expiring	set_transient() / delete_transient(), names suffixed per language	Theme search lists; includes/elementor-widget-compat.php; includes/admin/theme-transients.php
Theme cache-purge	Whole-site	admin-post.php?action=wpestate_purge_cache	includes/admin/cache-purge.php

Per-Request Static Caches

Runtime string lookups are hot-path code. They run on every gettext filter for every translated string on every page. To keep the database touch low, translation-runtime.php memoizes results inside each request:

// includes/translation-runtime.php function wpr_translate_domain_has_runtime_translations( $domain, $language_code ) { static $cache = array(); $cache_key = strtolower( $domain ) . '|' . strtolower( $language_code ); if ( array_key_exists( $cache_key, $cache ) ) { return (bool) $cache[ $cache_key ]; } // ... wpdb query against wp_wpestate_translation_strings ... $cache[ $cache_key ] = $found; return $found; }

function wpr_translate_lookup_runtime_translation( $domain, $original, $language_code ) {
static $cache = array();
$cache_key = strtolower( $domain ) . '|' . md5( $original ) . '|' . strtolower( $language_code );
if ( array_key_exists( $cache_key, $cache ) ) {
return $cache[ $cache_key ];
}
// ... wpdb query ...
$cache[ $cache_key ] = $value;
return $value;
}

Key design points:

Keys are lowercased and the original string is hashed with md5() so UTF-8 strings are safe in a static array.
Empty results are cached too. This matters: negative lookups dominate in the admin-only runtime override path.
There is no cross-request persistence here on purpose. Runtime string translation only applies in admin editor contexts (see wpr_translate_should_use_runtime_translations()), and each admin page load is short-lived.

If you add new lookup functions, follow the same pattern. Do not reach for wp_cache_set() here. These are request-scoped by design, and a persistent cache would make staleness harder to reason about.

Object Cache – Custom Field Preferences

The Custom Field Rules are loaded from a JSON configuration file and cached under the wpr_translate object cache group:

// includes/custom-fields-sync.php $option_name = 'wpr_cf_preferences'; $cache_key = 'wpr_cf_preferences'; $cache_group = 'wpr_translate';

wp_cache_set( $cache_key, $preferences, $cache_group );
$cached = wp_cache_get( $cache_key, $cache_group );

The priming flow (wpr_translate_prime_custom_fields_preferences_cache()) compares an md5 hash of the config file contents against the cached payload. If the file changed, the plugin re-reads the JSON, re-writes the wpr_cf_preferences option, and overwrites the cache entry.

Extending: If you ship a child plugin that writes to the same rules config, either call wpr_translate_sync_custom_fields_preferences() after your write, or invalidate directly with wp_cache_delete( ‘wpr_cf_preferences’, ‘wpr_translate’ ).

Per-Language Transients – Theme Search Lists

The WPResidence theme caches its large taxonomy lookup lists as transients. On a multilingual site each language has its own set. The helper wpestate_set_transient_name_multilang() (theme side) appends the active language to the transient name so callers never juggle suffixes manually.

The canonical cached keys (base names before language suffix):

wpestate_get_action_select_list wpestate_get_category_select_list wpestate_get_city_select_list wpestate_get_area_select_list wpestate_get_county_state_select_list wpestate_get_status_select_list wpestate_get_features_select_list

Invalidation is centralized in includes/admin/theme-transients.php:

// includes/admin/theme-transients.php function wpr_translate_admin_clear_theme_search_transients( $context ) { // Only act for the theme admin-strings domain (or the legacy 'wpresidence_admin'). // Build the list of language IDs (slug + code) from wpr_translate_get_active_languages(). foreach ( $keys as $key ) { delete_transient( $key ); // base, no language foreach ( $language_ids as $language_id ) { delete_transient( $key . '_' . $language_id ); // per-language variants } } }

This runs whenever admin-facing theme strings change, so translated dropdown labels stay in sync without manual purges. The function also honors ICL_LANGUAGE_CODE to cover sites migrating from WPML compatibility shims.

Elementor taxonomy widgets prime their own transients via the same multilang helper. See includes/elementor-widget-compat.php:

// includes/elementor-widget-compat.php $primed_transient_key = 'wpestate_elementor_tax_'; if ( function_exists( 'wpestate_set_transient_name_multilang' ) ) { $primed_transient_key = (string) wpestate_set_transient_name_multilang( $primed_transient_key ); } set_transient( $primed_transient_key, $primed_terms, 60 * 60 * 6 );

TTL is 6 hours. Invalidation is lazy. On the next language switcher render after expiry, the cache refills from the terms table.

Theme-Wide Cache Purge Endpoint

includes/admin/cache-purge.php exposes an AJAX bridge that triggers the WPResidence theme’s own purge action:

// includes/admin/cache-purge.php function wpr_translate_purge_wpestate_cache() { $purge_url = admin_url( 'admin-post.php' ); $nonce = wp_create_nonce( 'wpestate_purge_cache' ); // ... copies cookies for auth, POSTs to admin-post.php ... wp_remote_post( $purge_url, array( 'body' => array( 'action' => 'wpestate_purge_cache', '_wpnonce' => $nonce, ), // ... ) ); } add_action( 'wp_ajax_wpr_translate_purge_cache', 'wpr_translate_ajax_purge_cache' );

Called by the bulk auto-translate screen when a batch finishes. Gated by manage_options and a dedicated nonce (wpr_translate_purge_cache). Re-use this endpoint from your own admin flows after operations that touch many posts.

Query Filter & Cache Interaction

includes/query-filter.php applies the active language to WP_Query via pre_get_posts and the_posts. A few caching considerations follow from that:

Cached query results must be language-scoped. Anything you cache that wraps a WP_Query should include the active language code (or slug) in the cache key. Use the wpestate_set_transient_name_multilang() helper, or derive the code via wpr_translate_get_current_language().
suppress_filters bypasses language filtering. Callers that intentionally want cross-language results should set ‘suppress_filters’ => true or opt out via the plugin’s documented query vars. Never do this silently from inside a cached helper.
Avoid meta_key at WP_Query top level when not needed. It forces an INNER JOIN that silently drops posts without that key. Not a cache rule per se, but combined with caching it can freeze bad results.

Settings-Errors Transients

Admin screens use short-lived (30-second) settings_errors transients to carry notices across a redirect:

// includes/admin/menu.php, includes/admin/string-actions.php, includes/admin/reset-settings.php set_transient( 'settings_errors', get_settings_errors(), 30 );

These are unrelated to content caching. They are the standard WordPress pattern for post-submit notice survival. No invalidation needed. They self-expire.

Extension Points & Recipes

Adding a cached helper that depends on active language – key with wpestate_set_transient_name_multilang( ‘your_base_key’ ) so the plugin’s existing invalidators (see theme-transients.php) cover you when you pick compatible base names.
Bypassing cache for diagnostics – clear the static caches by forcing a fresh PHP process (new request); they have no public reset. For the object cache, use wp_cache_delete( ‘wpr_cf_preferences’, ‘wpr_translate’ ).
Clearing transients after bulk operations – call wpr_translate_admin_clear_theme_search_transients( ‘wpresidence_admin’ ). Pass the theme admin strings context to match the guard clause.
Flushing the whole theme cache – fire the AJAX endpoint wp_ajax_wpr_translate_purge_cache with the wpr_translate_purge_cache nonce, or call wpr_translate_purge_wpestate_cache() directly from PHP with an authenticated admin context.

Non-Latin Safety

All cache keys avoid sanitize_title() on user-supplied strings. Language codes go through sanitize_key(), translated values are hashed with md5() before being used as key fragments. Cyrillic, Arabic, and CJK language data caches identically to Latin data. There is no separate slow path.

Gotchas

Static caches do not clear on option save. If you write admin code that updates a translation mid-request and then reads it back, expect stale results in the same request. Re-query directly or reset the static in tests via a dedicated hook.
Transient TTLs are not adaptive. The 6-hour TTL on Elementor primed terms means a term renamed through WP admin might take up to 6 hours to reflect in some widgets, unless the plugin’s save hooks clear the specific key. Clear explicitly after bulk term updates.
The cache-purge endpoint is whole-site. Use it for post-batch jobs, not per-edit. You will hurt front-end performance if you call it on every save.
Reactivation does not clear transients. Activation runs flush_rewrite_rules() only. Stale caches survive deactivate/activate. Delete them explicitly if you need a clean slate.