MODX plugin to set Server-Timing header

modx.server-timing.plugin.php

<?php
// Run on event onWebPagePrerender
// Comma-separated list of strings like: cache;desc="Cache Read";dur=23.2  
// Expectation is duration is milliseconds  

$totalTime = $modx->startTime ? sprintf("%2.2f", (microtime(true) - $modx->startTime) * 1000) : 0;
$queryTime = isset($modx->queryTime) ? sprintf("%2.2f", $modx->queryTime * 1000) : 0;
$queries = isset($modx->executedQueries) ? $modx->executedQueries : 0;
$phpTime = sprintf("%2.2f", ($totalTime - $queryTime));

$source = $modx->resourceGenerated ? "database" : "cache";
$memory = number_format(memory_get_peak_usage(true) / (1024 * 1024), 0, ".", "");

$parts = [
    "total;desc=\"Total Execution Time\";dur={$totalTime}",
    "php;desc=\"PHP Execution Time\";dur={$phpTime}",
    "query;desc=\"Database Query Time\";dur={$queryTime}",
    // I'm unclear how to best handle non-duration values
    "queries;desc=\"Database Queries={$queries}\"",
    "source;desc=\"Source: {$source}\"",
    "memory;desc=\"Memory={$memory}MB\"",
];

$serverTiming = implode(",", $parts);
header("Server-Timing: {$serverTiming}");