custom-prometheus-exporter/index.php

<?php
require 'vendor/autoload.php';
require 'config.php';

if($_SERVER["REQUEST_URI"] == '/metrics' || php_sapi_name() == 'cli') {
    foreach ($config as $key => &$c) {
        if(isset($c['command'])) {
            $output=null;
            $retval=null;
            exec($c['command'], $output, $retval);
            $output = implode("\n", $output);
        } elseif(isset($c['http'])) {
            $client = new GuzzleHttp\Client();

            $options = [];
            $output = NULL;
            if (isset($c['http']['proxy'])) {
                $options['proxy'] = $c['http']['proxy'];
            }
            if (isset($c['http']['data']) && $c['http']['data'] == 'responsetime') {
                $options['on_stats'] = function (GuzzleHttp\TransferStats $stats) use (&$output) {
                    $output = $stats->getTransferTime();
                };
            }

            $hasresponse = NULL;
            try{
                $res = $client->request('GET', $c['http']['url'], $options);
                $hasresponse = true;
            } catch(GuzzleHttp\Exception\GuzzleException $e) {
                $hasresponse = false;
            }

            if (isset($c['http']['data']) && $c['http']['data'] == 'responsebody') {
                $output = $res->getBody()->getContents();
            } elseif (isset($c['http']['data']) && $c['http']['data'] == 'hasresponse') {
                $output = (int)$hasresponse;
            }
        }

        if(isset($c['jsonelem'])) {
            $c['value'] = getArrayValue($c['jsonelem'], json_decode($output, true));
        } else {
            $c['value'] = $output;
        }
    }

    $loader = new \Twig\Loader\FilesystemLoader('templates');
    $twig = new \Twig\Environment($loader, [
        'cache' => 'twig_cache',
    ]);
    echo $twig->render('metrics.twig', ['config' => $config]);
}

function getArrayValue($elem, $array) {
    $elem = explode('.', $elem);
    $new_array = $array;
    foreach ($elem as $i) {
        $new_array = $new_array[$i];
    }
    return $new_array;
}