wp_cache_get_last_changed() │ WP 4.7.0

Gets last changed date for the specified cache group.

No Hooks.

Return

String. UNIX timestamp with microseconds representing when the group was last changed.

Usage

wp_cache_get_last_changed( $group );

$group(string) (required): Where the cache contents are grouped.

Examples

#1 Example of using time tags when creating a cache

A stripped down piece of code from the kernel, which is used in the get_pages() function to cache its results.

function some_cache_orientated_function(){

	$key = md5( serialize( 'Some data, whatever' ) );

	$last_changed = wp_cache_get_last_changed( 'posts' );

	$cache_key = "get_pages:$key:$last_changed";

	// get the cache
	$cache = wp_cache_get( $cache_key, 'posts' );

	// there is a cache, let's bring it back
	if ( false !== $cache ) {
		return $pages;
	}

	$pages = $wpdb->get_results('SQL query for posts' );

	// keep only the ID
	$page_structure = array();
	foreach ( $pages as $page ) {
		$page_structure[] = $page->ID;
	}

	// no cache, get the data and save it in the cache
	wp_cache_set( $cache_key, $page_structure, 'posts' );

	return $pages;
}

Changelog

Since 4.7.0

Introduced.

`wp_cache_get_last_changed() wp cache get last changed` code ^{WP 6.1.1}

wp-includes/functions.php

function wp_cache_get_last_changed( $group ) {
	$last_changed = wp_cache_get( 'last_changed', $group );

	if ( ! $last_changed ) {
		$last_changed = microtime();
		wp_cache_set( 'last_changed', $last_changed, $group );
	}

	return $last_changed;
}