Simple PHP Cache

data.php

<?php

$cacheDir  = "cache";
$cacheFile = $cacheDir."/data-cache-".md5($_SERVER['QUERY_STRING']).".json";
$generFile = "data-generate.php";

if(!is_writable($cacheDir)){
    header($_SERVER['SERVER_PROTOCOL'] . ' 500 Internal Server Error', true, 500);
}

if (file_exists($cacheFile) and (time() - filemtime($cacheFile)) < 3600)
{
    $content = file_get_contents($cacheFile);
}
else
{
    ob_start();
    include $generFile;
    $content = ob_get_clean(); 
    $res     = file_put_contents($cacheFile, $content);
    touch($cacheFile);
}

echo $content;