custom-prometheus-exporter/index.php

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

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

			$options = [];
			if (isset($c['proxy'])) {
				$options['proxy'] = $c['proxy'];
			}

			$res = $client->request('GET', $c['httpurl'], $options);
			$output = $res->getBody()->getContents();
		} elseif(isset($c['httpresponsetime'])) {
			$client = new GuzzleHttp\Client();
			$output = NULL;

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

			$res = $client->request('GET', $c['httpresponsetime'], $options);
		}
		if(isset($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;
}