自动刷新由php中的缓存系统生成的页面html

Question

So I just found out the establishment of a system cache in php, but I need to understand one thing . I have an index.php file and I included this file has two files cache-top.php and cache-bottom.php and I generate an index.html file , I also change the name of my file index.php in first.php to fall on the index.html page when you enter the site. The system works well because I have a file that is generated, but I feel that the index.html file does not change after 2min as I configured in the "cache -top" file for refresh the content of index.html must refresh the page first.php and wanted to know if this is normal ? and what is a solution for the index.html file to refresh its content without refreshing first.php ?

cache-top.php code :

$expireTime = time () -120 ;
$caching = FALSE ;

$cacheFile = "index.html";

If( file_exists($cacheFile) ) {
    if (filemtime($cacheFile) < $expireTime) {
        ob_start();
    } else {      
        $caching = TRUE ;
         readfile($cacheFile);
    }
} else {
    ob_start() ;
}

thank you in advance