Page stats for administrators

<?php

add_action(
	'admin_bar_menu',
	static function ( $bar ) {
		if ( ! current_user_can( 'manage_options' ) ) {
			return;
		}
		$bar->add_node(
			array(
				'id'     => 'snipfire-stats',
				'parent' => 'top-secondary',
				'title'  => '<span id="snipfire-stats">…</span>',
			)
		);
	},
	200
);
// Filled in at the very end, when the numbers are final.
$snipfire_stats = static function () {
	if ( ! current_user_can( 'manage_options' ) || ! is_admin_bar_showing() ) {
		return;
	}
	$text = sprintf(
		'%s s · %d queries · %s MB',
		number_format_i18n( timer_float(), 2 ),
		get_num_queries(),
		number_format_i18n( memory_get_peak_usage() / MB_IN_BYTES, 1 )
	);
	echo '<script>( function () { var el = document.getElementById( "snipfire-stats" ); if ( el ) { el.textContent = ' . wp_json_encode( $text ) . '; } } )();</script>';
};
add_action( 'wp_footer', $snipfire_stats, 9999 );
add_action( 'admin_footer', $snipfire_stats, 9999 );