custom-prometheus-exporter/config.example.php

<?php
$config = [
	'app_demo_metric1' => [ // Key is being used a prometheus key
		'help' => 'Help text for metric',
		'command' => 'The command to be run',
		'jsonelem' => '0.metric', // The json element where the metric is found (Dot notated)
	],
	'app_demo_metric2' => [ 
		'help' => 'Help text for metric',
		'http' => [
            'url' => 'http://example.com', // The url to get collected for the metric
            'data' => 'responsebody' // The body is used as output
        ],
		'jsonelem' => '0.metric',
	],
    'app_demo_metric3' => [
        'help' => 'Help text for metric',
        'http' => [
            'url' => 'http://example.com', // The url to get collected for the metric
            'data' => 'hasresponse' // If an error occured during request this will return 0, otherwise 1
        ],
    ],
    'app_demo_metric4' => [
        'help' => 'Help text for metric',
        'http' => [
            'url' => 'http://example.com', // The url to get collected for the metric
            'data' => 'responsetime' // This will return the transfer time
        ],
    ],
];