PHP script to mock a response

index.php

<?php

function getRequestHeaders() {
    $headers = array();
    foreach($_SERVER as $key => $value) {
        $header = str_replace(' ', '-', ucwords(str_replace('_', ' ', strtolower($key))));
        $headers[$header] = $value;
    }
    return $headers;
}

$file_to_serve = basename($_GET['filename']) ?? (http_response_code(404) || die());
$header_text = "";
if ($_GET['debug']) {
    $headers = getRequestHeaders();
    $header_text .= "<br/>";
    foreach ($headers as $name => $value) {
        $header_text .= "$name: $value<br />\n";
    }
}

$handle = fopen($file_to_serve . ".header", "r");
if ($handle) {
    while (($line = fgets($handle)) !== false) {
        // process the line read.
        header($line);
    }

    fclose($handle);
} else {
    http_response_code(404);
    die();
}

$handle = fopen($file_to_serve . ".json", "r");
if ($handle) {
    while (($line = fgets($handle)) !== false) {
        // process the line read.
        print($line);
    }

    fclose($handle);
}
print($header_text);