i need to caching xml and json response requested to a remote host. Is There a simple Cache System developed in PHP?
If you are looking to get up and running right away, you can use APC, which is installed (or can be easily installed) with PHP, depending on what platform you are running PHP on. Then you can use the apc_add() function call to add keys into the cache.
Example:
<?php
$bar = 'BAR';
apc_add('foo', $bar);
?>
You can then use apc_exists() and apc_fetch() to check and fetch items out of the cache.
Obviously if your requirements are more complex, you may want to take a look at Memcached
PHP itself can't cache because it is interpreted at request time - there isn't any in-memory caching capabilities naively available. If you have control over the web server, you may be able to install APC cache. see this for a little info on how to use API. If not, you can check if that extension is installed (in my experience, not may hosts have this installed), ask for it to be installed, or simply grow your own (see below).
APC cache is a simple file-based caching mechanism that provides some neat facilities to expunge caches that grow old. You can build this yourself using the standard PHP library if APC isn't available (or you're doing something really simple). If you have to roll your own, use the above like as an implementation guide - build in the features you need and leave out what you don't. =)
Related
Is it possible to use apcu (as a php 5.5 module) in combination with suPHP?
The answer to What is best PHP Handler for APC says no:
suPHP also cannot work with an opcode caching extension such as eAccelerator or APC
but this post is over a year old and maybe not referring to apcu.
I can successfully enable the apcu module (in cPanel) and transfer content via apc_store and apc_fetch - but not between requests. It forgets what I've been storing when I reload the script/page.
So my first concern is to rule out if I'm trying something that's impossible anyway?
PS: for the record, What is userland caching APCu extension in PHP? gives some helpful background
Not possible.
suPHP runs each PHP request in a new process, so caching extensions that try to save data in memory across requests don't work. (Or, rather, they work, but any stored data is only accessible to that job, and is lost at the end of the request.)
Use something like memcached if you need data caching.
i'm new in PHP and want to try caching(for the first time), so i make website and it has :
dynamic home page
dynamic portfolio page
dynamic contact page
static about page
static admin page
so i read the tutorial about caching and i try to make my own caching system:
using file cache based on the what page is requested, when the page is requested the cache system will check if there's cache in cache directory if there's no cache file yet then write all the output(html) from the php script(in this case output from output buffer) and if there's cache file that corresponds with the specific id(based on URI) then just include_once() the html file.
Then i read in CodeIgniter(i make this website using CI) says there's APC for caching, then i read again about APC, what i read about APC is that it caches the DB results, but now i'm confused which should i use
what i get so far:
file caching probably would slower if there's alot of request (i dont know if this is true or not but i read it somewhere from search engine)
APC is fast
but i'm still confused which i should use , i'm on shared hosting
The levels of caching most relevant in a PHP application:
File / Script caching - The operating system will actually do this to a large extent. When a file is opened it's added to an OS-level cache. It stays there until the file is touched or the OS needs to free memory for other processes. A homegrown PHP solution isn't a good replacement for this.
Opcode caching - In order to function, PHP needs to parse and compile a script into opcodes. A mechanism like APC will cache the opcodes of every PHP script executed by Apache, provided that the cache doesn't overflow. A homegrown PHP solution build on top of APC can partially do this, but APC already does it ... so don't bother.
Query caching - If your script accesses a lot of data that doesn't change very frequently, or wherein some latency between updates and the visibility of those updates is acceptable, caching the results from complex queries is beneficial. A homegrown PHP solution built on APC is acceptable and beneficial at this level. But a database level solution is also appropriate here, and often more appropriate.
Output caching - If your page is largely deterministic and/or the same sort of latency applicable to query caching is acceptable, you can cache the entire output of the script using output buffering and APC. A homegrown PHP solution built on APC is acceptable here, but generally not necessary. If the page is static, you're probably not saving yourself any re-computation. And if it's dynamic, it's usually preferable to just re-render the page anyway.
In a dedicated or virtual-dedicated environment you'd need install APC (or something similar) yourself. But, in a shared hosting environment, it's very likely that APC is installed. And if it weren't you couldn't install it yourself anyway.
And, due to my own uncertainty, I'd recommend not performing any query or output caching with APC in a shared environment -- I'm not sure whether APC segregates caches by virtual host. Even if it does, I wouldn't assume that my site is truly a separate virtual host.
It seems that PHP has two memcached libraries named memcache and memcached. What is the difference and how do you know which one to use? Is one outdated? It seems that memcached offers more methods so I would assume that means it has had the most development - but it also seems to require external C/C++ libraries so I'm not sure if I can install it.
It seems that memcache has been around longer, does not require additional libraries, and has pre-compiled binaries for even windows! I would think that it would be the better choice for now. However, being new to memcached (server) I'm not sure if there is some super important features in memcached (php) that make it worth the extra trouble.
Memcached client library was just recently released as stable. It is being used by digg ( was developed for digg by Andrei Zmievski, now no longer with digg) and implements much more of the memcached protocol than the older memcache client. The most important features that memcached has are:
Cas tokens. This made my life much easier and is an easy preventive system for stale data. Whenever you pull something from the cache, you can receive with it a cas token (a double number). You can than use that token to save your updated object. If no one else updated the value while your thread was running, the swap will succeed. Otherwise a newer cas token was created and you are forced to reload the data and save it again with the new token.
Read through callbacks are the best thing since sliced bread. It has simplified much of my code.
getDelayed() is a nice feature that can reduce the time your script has to wait for the results to come back from the server.
While the memcached server is supposed to be very stable, it is not the fastest. You can use binary protocol instead of ASCII with the newer client.
Whenever you save complex data into memcached the client used to always do serialization of the value (which is slow), but now with memcached client you have the option of using igbinary. So far I haven't had the chance to test how much of a performance gain this can be.
All of this points were enough for me to switch to the newest client, and can tell you that it works like a charm. There is that external dependency on the libmemcached library, but have managed to install it nonetheless on Ubuntu and Mac OSX, so no problems there so far.
If you decide to update to the newer library, I suggest you update to the latest server version as well as it has some nice features as well. You will need to install libevent for it to compile, but on Ubuntu it wasn't much trouble.
I haven't seen any frameworks pick up the new memcached client thus far (although I don't keep track of them), but I presume Zend will get on board shortly.
UPDATE
Zend Framework 2 has an adapter for Memcached which can be found here
When using Windows, the comparison is cut short: memcache appears to be the only client available.
Memcached is a newer API, it also provides memcached as a session provider which could be great if you have a farm of server.
After the version is still really low 0.2 but I have used both and I didn't encounter major problem, so I would go to memcached since it's new.
This is 2013. Forget about the 2009 comments. Likewise, if you are running serious traffic loads, do not even contemplate how to make-do with a windows based memcache.
When dealing with a very large scale (500+ front end web servers) and 20+ back end database servers and replicants (mysql & mssql mix), a farm of memcached servers (12 servers in group) supports multiple high volume OLTP applications answering 25K ~ 40K mc->get calls per-second. These calls are those that do NOT have to reach a database.
IMHO, this use of memcached provided SERIOUS $$$,$$$savings on CAPEX for new DB servers & licences as well as on support contracts for large commercial designs.
A friend has recommended that I install php APC, claiming it will help php run faster and use less memory
sounds promising but I'm a little nervous about adding it to my VPS server
I have one small app that I've built using codeigniter, and several sites that use the popular slideshowpro photo gallery software
could install this break any of the back end code on my sites?
I'm no high tech server guy, but should I give this a try?
Depends entirely on your situation.
Is your site unresponsive or slow at the moment? Is this definitely due to the PHP scripts and not any other data sources such as a database or remote API?
If you answered yes to the above, then installing one of the many PHP accelerators out there would be a good shout. As for using less memory, that's largely dependent on your apache/lightppd/nginx config and php.ini variables.
Most PHP accelerators work by converting the (to be) interpreted PHP code into opcode. This is then stored in memory (RAM) for fast access. If you haven't already implemented file-based caching in CodeIgniter then the benefits of installing a PHP accelerator would be noticeable. If you haven't, then I suggest you do that first before moving straight over to (wasting?) spending time trying to install APC manually.
If your site is currently performing well and you're not too confident in your *nix skills then I suggest you try implementing CodeIgniter caching first rather than try messing with what is an already working VPS.
My personal preference is PHP eAccelerator.
Should installing a PHP cache engine not improve your site's performance then I suggest you look at what other factors influence your application. As stated above, these could be: database or API to name a few.
Hope this helps.
APC is basically a cache engine that stores your compiled php scripts on a temp location on your server. Meaning that these do not have to be interpreted every time someone calls your sccript. It is a PHP extension can can safely be turned ON or OFF and it does not affect your actual code. So... do not fear!
When a php script is processed, there is a compilation phase, where php converts the source code of the php files into "opcodes". APC simply caches the result of this compilation phase, so it should be safe to turn on.
That said, when making such changes to production code it is always wise to run a regression test to ensure no new issues have been introduced.
I'm currently implementing memcached into my service but what keeps cropping up is the suggestion that I should also implement APC for caching of the actual code.
I have looked through the few tutorials there are, and the PHP documentation as well, but my main question is, how do I implement it on a large scale? PHP documentation talks about storing variables, but it isn't that detailed.
Forgive me for being uneducated in this area but I would like to know where in real sites this is implemented. Do I literally cache everything or only the parts that are used often, such as functions?
Thanks!
As you know PHP is an interpreted language, so everytime a request arrives to the server it need to open all required and included files, parse them and execute them. What APC offers is to skip the require/include and parsing steps (The files still have to be required, but are stored in memory so access is much much faster), so the scripts just have to be executed. On our website, we use a combination of APC and memcached. APC to speed up the above mentioned steps, and memcached to enable fast and distributed storing and accessing of both global variables (precomputed expensive function calls etc that can be shared by multiple clients for a certain amount of time) as well as session variables. This enables us to have multiple front end servers without losing any client state such as login status etc.
When it comes to what you should cache... well, that really depends on your application. If you have a need for multiple frontends somewhere down the line, I would try to go with memcached for such caching and storing, and use APC as an opcode cache.
APC is both an opcode cache and a general data cache. The latter works pretty much like memcached, whereas the opcode cache works by caching the parsed php-files, so that they won't have to be parsed on each request. That can generally speed up execution time up quite a bit.
You don't have to implement the opcode caching features of APC, you just enable them as a php module.
APC cache size and other configuration information is here.