Control Varnish cache time from php script

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It is possible in Varnish to use ESI tags to give multiple sections on your page different cache times.

Using varnish 4

For example : index.php

<html>...

<?php  
// Cached as normal in Varnish ( 120 seconds)
 echo " Date 1 (cached): ".date('Y/m/d H:i:s') ."\n";
 ?>

<esi:include src="inc/sidebar.php"/>
<esi:remove>
  <?php include('inc/sidebar.php'); ?>
  <p>Not ESI!</p> 
</esi:remove>

sidebar.php

<?php
 echo "<br>NOT CACHED : ".date('Y/m/d H:i:s');
?>

Config Varnish ( default.vcl)

sub vcl_backend_response { 
  set beresp.do_esi = true;
  ## if sidebar remove cache  else 120 seconds cache 
  if (bereq.url ~ "sidebar.php") { 
     ## set beresp.ttl = 0s; 
     set beresp.uncacheable = true; 
     return(deliver);  
  } else { 
    set beresp.ttl = 120s; 
 }

The above works fine , but I would love to find a way to control this from within my projects. If I get a lot of ESI files this config file would get huge.

I thought about this :

In index.php, as first thing :

<?php
header('Cache-Control: max-age=120');
?>

in sidebar.php

<?php
 header('Cache-Control: max-age=0');
 echo "<br>NOT CACHED : ".date('Y/m/d H:i:s');
?>

In config ( default.vcl )

import std;
sub vcl_backend_response { 
    set beresp.do_esi = true;
# Set total cache time from cache control or 120 seconds.
    set beresp.ttl = std.duration(regsub(beresp.http.Cache-Control, ".*max-age=([0-9]+).*", "\1") + "s", 120s);

    ## Debug , shows up in header.
    set beresp.http.ttl =beresp.ttl;
}

Now this works partially.. If I only put in the header max-age in the index.php , it will control the time this page will get cached. The big problem is that sidebar.php ( max-age=0 ) overwrites all and so the whole page is not cached.

Does anyone know a solution.. The thing that matters is to control cache time ( beresp.ttl ) from within a php script.

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