Php header http cache

How to use http cache headers with php

Solution 3: I’m not familiar with this tool, however until any browser has fetched content with caching headers it won’t be able to cache it. Solution: What is Cache? Cache-Control is an HTTP cache header, Which simply Makes your website Faster, Also it can help your website when using Private Info.

How to use HTTP cache headers with PHP

You might want to use private_no_expire instead of private , but set a long expiration for content you know is not going to change and make sure you process if-modified-since and if-none-match requests similar to Emil’s post.

$tsstring = gmdate('D, d M Y H:i:s ', $timestamp) . 'GMT'; $etag = $language . $timestamp; $if_modified_since = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ? $_SERVER['HTTP_IF_MODIFIED_SINCE'] : false; $if_none_match = isset($_SERVER['HTTP_IF_NONE_MATCH']) ? $_SERVER['HTTP_IF_NONE_MATCH'] : false; if ((($if_none_match && $if_none_match == $etag) || (!$if_none_match)) && ($if_modified_since && $if_modified_since == $tsstring)) < header('HTTP/1.1 304 Not Modified'); exit(); >else < header("Last-Modified: $tsstring"); header("ETag: \"\""); > 

Where $etag could be a checksum based on the content or the user ID, language, and timestamp, e.g.

$etag = md5($language . $timestamp); 

You must have an Expires header. Technically, there are other solutions, but the Expires header is really the best one out there, because it tells the browser to not recheck the page before the expiration date and time and just serve the content from the cache. It works really great!

It is also useful to check for a If-Modified-Since header in the request from the browser. This header is sent when the browser is «unsure» if the content in it’s cache is still the right version. If your page is not modified since that time, just send back an HTTP 304 code (Not Modified). Here is an example that sends a 304 code for ten minutes:

You can put this check early on in your code to save server resources.

Take your pick — or use them all! 🙂

header('Expires: Thu, 01-Jan-70 00:00:01 GMT'); header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT'); header('Cache-Control: no-store, no-cache, must-revalidate'); header('Cache-Control: post-check=0, pre-check=0', false); header('Pragma: no-cache');

Http cache by vary on a custom header, I’m researching http cache by using Vary header, my website has to serve a response content base on a user preferred currency,

Cache Control headers not doing the JOB

What is Cache?

Cache-Control is an HTTP cache header, Which simply Makes your website Faster, Also it can help your website when using Private Info.

How to see if my website is caching?

Inspect Elements -> Network -> click on the image / file -> Responses Header -> cache-control

Settings Up cache

 Header set Cache-Control "max-age=84600, public" 

location ~* \.(js|css|png|jpg|jpeg|gif|ico)$

I dont Want Cache

In that case you need to use :

If you dont see This taking effect, first try using it on another browser or removing your cache

Using Meta Tags

Checking if my Website is cached

#1 — Is cached #2 — Is not cached

How to prevent Browser cache for php site, try this

How to use control-cache headers?

The key is must-revalidate : This means, that the client is asking the server if the file has changed. If you don’t handle this case, the browser will fetch a new copy.

Read Mark Nottingham’s fantastic Caching Tutorial for more information. As an example for a PHP implementation you may use my code.

Look into $_SERVER[‘HTTP_IF_NONE_MATCH’] and $_SERVER[‘HTTP_IF_MODIFIED_SINCE’] for validating clients. And be aware that both headers may contain malicious code. 😉

When it says from cache: false does that mean from the server cache and not the client’s cache?

^ This is referring to the client cache.

Setting up caching in this manner will cover your PHP files, but you’ll need to implement something else server side to cache your images, CSS, scripts, etc. This can be done using .htaccess, if your server supports it.

For example, this is what I’m using in my .htaccess file for a couple sites.

 Header set Expires "Thu, 15 Apr 2012 20:00:00 GMT" Header unset ETag FileETag None 

I’m not familiar with this tool, however until any browser has fetched content with caching headers it won’t be able to cache it. It appears that your server is sending back the expected headers and the page should be cached by the browser — your browser should now have a copy in its cache. If you try fetching the same page again then it will be fetched from the cache rather than the origin server (assuming the 1 hour time limit hasn’t expired).

Note that some browsers will interpret a refresh request as an explicit request to ignore the cache and fetch the page again — try accessing it via link rather than hitting the refresh button.

Client Cache — Microsoft Docs, Content that contains a «no-cache» header should not be cached by any entity. — Content that contains a «private» header should not be cached by

Proper cache headers to ensure PHP pages are always re-fetched

I believe your assumptions are correct. I’ve done a lot of projects involving dynamic data and we never needed anything more than Cache-Control: no-cache (a HTTP/1.1 header). Setting an Expires: date in the past is also good practice to cover HTTP/1.0 user agents.

That said, if you want to specifically inform requesting agents that the page is definitely distinct from the previous access, it might be worth sending an Etag: header which is time-based. That way, any previously fetched copy will have a different Etag and the agent will be aware that the copy now being sent is new. This will marginally increase request header size as the request will contain the previous Etag if any.

Cache control and expires header for PHP, ‘ GMT’; if ($if_modified_since == $gmdate_mod) < header("HTTP/1.0 304 Not Modified"); exit; >header(«Last-Modified: $gmdate_mod»); header(‘

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Setting HTTP Cache Headers with PHP

If you are just taking modern browsers into consideration, you need to set only «Cache-Control» and «ETag» headers. «Expires» and «Last-Modified» headers belong to an older HTTP specification and you can leave them out.

This tutorial will discuss how you can set «Cache-Control» and «ETag» headers through PHP.

For an understanding about HTTP caching in general, you can refer HTTP Cache Headers Explained and Practical Examples of Cache Headers.

Setting «Cache-Control» Header

Setting the «Cache-Control» header is direct. Just use the required directives for «Cache-Control» and send the header through the header function.

header('Cache-Control: max-age=86400');

Please note that you must use this function before any output from the script is emitted.

Setting «ETag» Header

Since the ETag header should be unique for a unique content, it requires a little logic. This tutorial dicusses one method based on timestamps through which you can create ETags — however this is just for example and you can use your own methods to create ETags. ETags based on a hash of the content are also popular.

2 timestamps can be related with a PHP script :

• Generally PHP scripts send out dynamic content — for example some content from the database. That content usually has a last modified timestamp, which is also stored in the database.
• Another timestamp is associated with the code contained in the PHP script — basically the timestamp when the PHP file was last modified.

As an example, see the below 2 codes. The first one is the content of a PHP file at some time. The second one is the content of the same PHP file, but after some time (someone made a modification to the code).

The main content that the user sees is same for both, but the content of the PHP files are different (an extra script tag). So while creating ETags based on last modification timestamp, we will have to consider this also.

So we set the ETag as the concatatenation of the last modification timestamp of the main content (that user sees) AND the last modification timestamp of the PHP file (in the server filesystem). If any of these timestamps change, the ETag is changed.

Last modification timestamp of the PHP file in the server file system can be retrieved through the filemtime function.

PHP Codes to Set Cache Headers

 content is the same as browser cache // So send a 304 Not Modified response header and exit if($_SERVER['HTTP_IF_NONE_MATCH'] == $etag) < header('HTTP/1.1 304 Not Modified', true, 304); exit(); >> // Rest of the code in the PHP script ?> 

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