WordPress: Print some debug infos into backend footer.

plugin.php

/**
 * For site admins: Print some debug infos into backend footer.
 *  - Time
 *  - DB Queries
 *  - Memory Usage
 *  - Cache Hts/Misses
 *  - Active Plugins
 *
 * @param  string $text Existing footer text.
 *
 * @return string       Footer text with infos.
 */
function ds_footer_debug_infos( $text ) {
	if ( ! is_super_admin() )
		return $text;

	$text  = 'Time : ' . timer_stop( 0 ) . ' | ';
	$text .= 'DB Queries: ' . $GLOBALS['wpdb']->num_queries . ' | ';
	$text .= 'Memory: ' . number_format( ( memory_get_peak_usage()/1024/1024 ), 1, ',', '' ) . '/' . ini_get( 'memory_limit' ) . ' | ';

	$ch = empty( $GLOBALS['wp_object_cache']->cache_hits ) ? 0 : $GLOBALS['wp_object_cache']->cache_hits;
	$cm = empty( $GLOBALS['wp_object_cache']->cache_misses ) ? 0 : $GLOBALS['wp_object_cache']->cache_misses;
	$text .= 'Cache Hits: ' . $ch . ' | Cache Misses: ' . $cm . ' | ';

	$ap = count( get_option('active_plugins') );
	$text .= 'Active Plugins: ' . $ap;


	return $text;
}
add_filter( 'admin_footer_text', 'ds_footer_debug_infos' );