get_site_transient( string $transient ): mixed

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$transientstring

Transient name. Expected to not be SQL-escaped.

Return value

mixed

Value of transient.

Code examples

Every example is editable and runs in a real WordPress booted in your browser by WordPress Playground. Press Run, then edit the code: clicking away re-runs it. Nothing is sent anywhere until you do.

$updates = get_site_transient( 'update_plugins' );

if ( false === $updates ) {
	echo esc_html( 'No cached plugin update data yet.' );
} else {
	echo '<pre>' . esc_html( print_r( $updates, true ) ) . '</pre>';
}

$cache_key = 'my_plugin_published_post_count';
$count = get_site_transient( $cache_key );

if ( false === $count ) {
	$count = wp_count_posts()->publish;
	set_site_transient( $cache_key, $count, 10 * MINUTE_IN_SECONDS );
	echo esc_html( 'Calculated fresh count: ' . $count );
} else {
	echo esc_html( 'Read cached count: ' . $count );
}

Common problems and fixes · 3

• Why does get_site_transient() return false even right after I called set_site_transient() with the same key?
• How do I know if the transient truly doesn't exist versus it was intentionally stored as false?
• Why doesn't my update_plugins or update_themes site transient ever seem to expire?

Alternatives and related functions

get_transient

When the cached value only needs to apply to the current site rather than the whole network.

set_site_transient

When you need to store or refresh the value that get_site_transient() will later read back.

delete_site_transient

When you need to invalidate a cached value immediately instead of waiting for its expiration, especially for the update_core, update_plugins, and update_themes keys that never time out.

get_site_option

When you need persistent site-wide data with no expiration at all, rather than a value meant to go stale.

Performance profile

How much work a call to get_site_transient() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Moderate

Reads stored settings via get_site_option(), cached per request but not free on a cold cache.

Scaling

Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions

11–55

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 62.

Plugin surface

2 hooks

Third-party callbacks on 'pre_site_transient_{$transient}', 'site_transient_{$transient}' run inside this call, and their cost is not bounded by anything here.

Called by

50

50 places in core call this, so the cost is paid more often than your own code shows.

What it touches

• transienttransientget_site_transient()this function does it
• hookthird-party callbacksapply_filters()called directly
• cacheobject cachewp_cache_get()called directly
• optionnetwork optionget_site_option()called directly

Further down the call graph this can also reach serialize and query. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 10 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost get_site_transient() can have, taken from its control-flow graph on PHP 8.5.

Hooks and filters fired · 2

2 hooks fire while get_site_transient() runs, in this order:

1. 1
   apply_filters( pre_site_transient_{$transient} )filterline 2582 (+18 into the body)

   Filters the value of an existing site transient before it is retrieved.

2. 2
   apply_filters( site_transient_{$transient} )filterline 2622 (+58 into the body)

   Filters the value of an existing site transient.

Uses · 7

• apply_filters()Calls the callback functions that have been added to a filter hook.
• wp_using_ext_object_cache()Toggles `$_wp_using_ext_object_cache` on and off without directly touching global.
• wp_installing()Checks or sets whether WordPress is in "installation" mode.
• wp_cache_get()Retrieves the cache contents from the cache by key and group.
• wp_prime_site_option_caches()Primes specific network options for the current network into the cache with a single database query.
• get_site_option()Retrieve an option value for the current network based on name of option.
• delete_site_option()Removes an option by name for the current network.

Used by · 50

• Plugin_Upgrader::bulk_upgrade()Upgrades several plugins at once.
• Plugin_Upgrader::upgrade()Upgrades a plugin.
• Theme_Upgrader::bulk_upgrade()Upgrades several themes at once.
• Theme_Upgrader::upgrade()Upgrades a theme.
• WP_Automatic_Updater::run()Kicks off the background update process, looping through all pending updates.
• WP_Community_Events::get_cached_events()Gets cached events.
• WP_Debug_Data::get_wp_active_theme()Gets the WordPress active theme section of the debug data.
• WP_Debug_Data::get_wp_parent_theme()Gets the WordPress parent theme section of the debug data.
• WP_Debug_Data::get_wp_plugins_raw_data()Gets the raw plugin data for the WordPress active and inactive sections of the debug data.
• WP_Debug_Data::get_wp_themes_inactive()Gets the WordPress inactive themes section of the debug data.
• WP_Feed_Cache_Transient::load()Retrieves the data saved in the transient.
• WP_Feed_Cache_Transient::mtime()Gets mod transient.

Source code

View on Trac ↗View on GitHub ↗

2564function get_site_transient( $transient ) {2565 2566	/**2567	 * Filters the value of an existing site transient before it is retrieved.2568	 *2569	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.2570	 *2571	 * Returning a value other than boolean false will short-circuit retrieval and2572	 * return that value instead.2573	 *2574	 * @since 2.9.02575	 * @since 4.4.0 The `$transient` parameter was added.2576	 *2577	 * @param mixed  $pre_site_transient The default value to return if the site transient does not exist.2578	 *                                   Any value other than false will short-circuit the retrieval2579	 *                                   of the transient, and return that value.2580	 * @param string $transient          Transient name.2581	 */2582	$pre = apply_filters( "pre_site_transient_{$transient}", false, $transient );2583 2584	if ( false !== $pre ) {2585		return $pre;2586	}2587 2588	if ( wp_using_ext_object_cache() || wp_installing() ) {2589		$value = wp_cache_get( $transient, 'site-transient' );2590	} else {2591		// Core transients that do not have a timeout. Listed here so querying timeouts can be avoided.2592		$no_timeout       = array( 'update_core', 'update_plugins', 'update_themes' );2593		$transient_option = '_site_transient_' . $transient;2594		if ( ! in_array( $transient, $no_timeout, true ) ) {2595			$transient_timeout = '_site_transient_timeout_' . $transient;2596			wp_prime_site_option_caches( array( $transient_option, $transient_timeout ) );2597 2598			$timeout = get_site_option( $transient_timeout );2599			if ( false !== $timeout && $timeout < time() ) {2600				delete_site_option( $transient_option );2601				delete_site_option( $transient_timeout );2602				$value = false;2603			}2604		}2605 2606		if ( ! isset( $value ) ) {2607			$value = get_site_option( $transient_option );2608		}2609	}2610 2611	/**2612	 * Filters the value of an existing site transient.2613	 *2614	 * The dynamic portion of the hook name, `$transient`, refers to the transient name.2615	 *2616	 * @since 2.9.02617	 * @since 4.4.0 The `$transient` parameter was added.2618	 *2619	 * @param mixed  $value     Value of site transient.2620	 * @param string $transient Transient name.2621	 */2622	return apply_filters( "site_transient_{$transient}", $value, $transient );2623}

Changelog

Introduced in 2.9.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/option.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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