simplelog.php

<?php

$fp = fopen(__DIR__.'/logs/access.log', 'a');

$headers = [];
foreach($_SERVER as $name => $value) {
    if (preg_match('/^HTTP_.*/', $name)) {
        $headers[$name] = $value;
    }
}

$logData = [
    date('Y-m-d H:i:s'),
    $_SERVER['HTTP_HOST'],
    $_SERVER['REQUEST_URI'],
    json_encode($_POST, JSON_UNESCAPED_UNICODE),
    json_encode($headers, JSON_UNESCAPED_UNICODE)
];

fwrite($fp, implode("\t", $logData)."\n");

fclose($fp);