Webhook logging script

webhook-log.php

<?php
# This PHP script accepts all JSON POST bodies and stores these to a specified log file.
# You could then run `tail -f /var/log/whlog | jq` to tail pretty-printed JSON logs as these arrive

# must be writable for the PHP process
$log_filename = '/var/log/whlog';

if (!is_writable($log_filename)) {
    http_response_code(500);
    echo "Log file is not writable";
    exit;
}

// validates a JSON formatted string
function is_valid_json($json_str)
{
    if (!isset($json_str) || empty($json_str) || strlen($json_str) == 0) {
        return false;
    }
    json_decode($json_str);
    return json_last_error() == JSON_ERROR_NONE;
}

if ($_SERVER['REQUEST_METHOD'] == "POST") {
    $post_body = file_get_contents("php://input");
    if ($post_body) {
        // Make sure the request content is always a valid JSON string
        if (!is_valid_json($post_body)) {
            $post_body = json_encode(array('error' => 'invalid_json', content => $post_body));
        }

        file_put_contents($log_filename,
            // jq is not able to handle non-JSON lines so include request metadata
            // also as part of the JSON entry
            json_encode(array(
                'time' => date('c'),
                'remote_addr' => $_SERVER['REMOTE_ADDR'],
                'content_type' => isset($_SERVER["CONTENT_TYPE"]) ? trim($_SERVER["CONTENT_TYPE"]) : '',
                'request' => json_decode($post_body),
            )) . "\n",
            FILE_APPEND);
    }
}

echo "OK";