Im having a problem that is slowing down some of my ajax requests.
Using jquery I make an ajax call to a php script that queries the database runs some scripts and then returns the data.
Since im querying lots of data and formatting as well sometimes it takes 3-8 secs to return and decreases user experience.
How can I cache my php so it can return a cache result and only refresh the cache when a user makes a change.
Also some querys return different results based on what user is logged in. So I would need to cache the php ajax request/per user.
Here is some information about MySql caching in PHP
My approach would be to use Zend_Cache to cache the returned code. A sample workflow would be:
$cache = Zend_Cache::factory($frontendName,
$backendName,
$frontendOptions,
$backendOptions);
$data = $cache->load('member-'.$id);
if (false === $data) {
{.. process normally populating $data ..}
$cache->save($data, 'member-'.$id);
}
{.. return $data formatted ..}
To remove the cached data if its been updated:
$cache = Zend_Cache::factory($frontendName,
$backendName,
$frontendOptions,
$backendOptions);
$cache->remove('member-'.$id);
Reference http://framework.zend.com/manual/en/zend.cache.html
Time to install memcache: http://php.net/manual/en/book.memcache.php
Related
I have a function that generates a table with contents from the DB. Some cells have custom HTML which I'm reading in with file_get_contents through a templating system.
The small content is the same but this action is performed maybe 15 times (I have a limit of 15 table rows per page). So does file_get_contents cache if it sees that the content is the same?
file_get_contents() does not have caching mechanism. However, you can use write your own caching mechanism.
Here is a draft :
$cache_file = 'content.cache';
if(file_exists($cache_file)) {
if(time() - filemtime($cache_file) > 86400) {
// too old , re-fetch
$cache = file_get_contents('YOUR FILE SOURCE');
file_put_contents($cache_file, $cache);
} else {
// cache is still fresh
}
} else {
// no cache, create one
$cache = file_get_contents('YOUR FILE SOURCE');
file_put_contents($cache_file, $cache);
}
UPDATE the previous if case is incorrect, now rectified by comparing to current time. Thanks #Arrakeen.
Like #deceze says, generally the answer is no. However operating system level caches may cache recently used files to make for quicker access, but I wouldn't count on those being available. If you'd like to cache a file that is being read multiple times per request, consider using a static variable to act as a cache inside a wrapper function.
function my_file_read($filename) {
static $file_contents = array();
if (!isset($file_contents[$filename])) {
$file_contents[$filename] = file_get_contents($filename);
}
return $file_contents[$filename];
}
Calling my_file_read($filename) multiple times will only read the file from disk a single time, subsequent calls will read the value from the static variable within the function. Note that you shouldn't count on this approach for large files or ones used only once per page, since the memory used by the static variable will persist until the end of the request. Keeping the contents of files unnecessarily in static variables is a good way to make your script a memory hog.
The correct answer is yes. All the PHP file system functions do their own caching, and you can use the "realpath_cache_size = 0" directive in PHP.ini to disable the caching if you like. The default caching timeout is 120 seconds. This is separate from the caching typically done by browsers for all GET requests (the majority of Web accesses) unless the HTTP headers override it. Caching is not a good idea during development work, since your code may read in old data from a file whose contents you have changed.
I would like to limit the number of times a page is generated in a certain time frame, but am unsure of how to even approach the problem.
Previously, I have solved similar problems by scheduling the pages to be generated and saved in a cron job, but this will not allow me to do this dynamically.
Here is the scenario:
I have n number of user created rooms. I would like to build a JSON api to allow the users to access room information for use on their own pages. However, generating a new JSON result for every request would be extremely inefficient and impose security risks on the database server. I would like to limit it, so that all requests in x amount of time use the same JSON result rather than new results each time.
a simple caching system can be done like this
if (!file_exists($cacheFile) || filemtime($cacheFile) - time() > $cacheLifetime){
//generate json and save to $cacheFile
}
header("Content-Type: application/json");
header("Content-Length: ".filesize($cacheFile));
readfile($cacheFile);
This problem is a typical use case for a cache.
The general algorithm is (when a resource is requested):
if (resource is cached) {
return cached contents
} else {
construct the resource
store resource in cache
return the resource
}
If you want to implement a time-based invalidation, the algorithm becomes:
if (resource is cached) {
if (cached resource older than threshold) {
remove resource from cache
} else {
return cached contents
}
}
construct the resource
store resource in cache
return the resource
The "age" of the cached contents is calculated from the date of creation of this content, that you need to store along with the cache entry.
Depending on how dynamic your users web-sites are, you may also want to not regenerate the JSON if "nothing has changed" since the last generation. Your algorithm would then become:
if (resource is cached) {
if (cached resource older than threshold AND something changed) {
remove resource from cache
} else {
return cached contents
}
}
...
The meaning of "nothing / something has changed" is up to you, it could be the user posts new contents, or some statistics are updated or whatever is used to build your resource. Set a flag on the cache when such an event happens.
The cache can take any form: a flat file on the server, a database row, a session variable, etc.
Use a database to cache the json strings (dont forget a timestamp). Then you are able to search your database first and provide the already generated JSON-string :)
I want to set up a simple cache feature with php. I want the script to get data from somewhere, but not to do it on every page view, but only every hour.
I know i can have a cron job that runs a php script every hour.
But I was wondering if this can be achieved without cron, just inside the php script that created the page based on the data fetched (or cached). I'm really looking the simplest solution possible. It doesn't have to be accurate
I would use APC as well, but in either case you still need some logic. Basic file cache in PHP:
if (file_exists($cache_file) and time() - filemtime($cache_file) < 3600)
{
$content = unserialize(file_get_contents($cache_file));
}
else
{
$content = your_get_content_function_here();
file_put_contents($cache_file, serialize($content));
}
You only need to serialize/unserialize if $content is not a string (e.g. an array or object).
Why just don't use APC ?
you can do
apc_store('yourkey','yourvalue',3600);
And then you can retrive the content with:
apc_fetch();
On my website there is a php function func1(), which gets some info from other resources. It is very costly to run this function.
I want that when Visitor1 comes to my website then this func1() is executed and the value is stored in $variable1=func1(); in a text file (or something, but not a database).
Then a time interval of 5 min starts and when during this interval Visitor2 visits my website then he gets the value from the text file without calling the function func1().
When Visitor3 comes in 20 min, the function should be used again and store the new value for 5 minutes.
How to make it? A small working example would be nice.
Store it in a file, and check the file's timestamp with filemtime(). If it's too old, refresh it.
$maxage = 1200; // 20 minutes...
// If the file already exists and is older than the max age
// or doesn't exist yet...
if (!file_exists("file.txt") || (file_exists("file.txt") && filemtime("file.txt") < (time() - $maxage))) {
// Write a new value with file_put_contents()
$value = func1();
file_put_contents("file.txt", $value);
}
else {
// Otherwise read the value from the file...
$value = file_get_contents("file.txt");
}
Note: There are dedicated caching systems out there already, but if you only have this one value to worry about, this is a simple caching method.
What you are trying to accomplish is called caching. Some of the other answers you see here describe caching at it's simplest: to a file. There are many other options for caching depending on the size of the data, needs of the application, etc.
Here are some caching storage options:
File
Database/SQLite (yes, you can cache to a database)
MemCached
APC
XCache
There are also many things you can cache. Here are a few:
Plain Text/HTML
Serialized data such as PHP objects
Function Call output
Complete Pages
For a simple, yet very configurable way to cache, you can use the Zend_Cache component from the Zend Framework. This can be used on it's own without using the whole framework as described in this tutorial.
I saw somebody say use Sessions. This is not what you want as sessions are only available to the current user.
Here is an example using Zend_Cache:
include ‘library/Zend/Cache.php’;
// Unique cache tag
$cache_tag = "myFunction_Output";
// Lifetime set to 300 seconds = 5 minutes
$frontendOptions = array(
‘lifetime’ => 300,
‘automatic_serialization’ => true
);
$backendOptions = array(
‘cache_dir’ => ‘tmp/’
);
// Create cache object
$cache = Zend_Cache::factory(‘Core’, ‘File’, $frontendOptions, $backendOptions);
// Try to get data from cache
if(!($data = $cache->load($cache_tag)))
{
// Not found in cache, call function and save it
$data = myExpensiveFunction();
$cache->save($data, $cache_tag);
}
else
{
// Found data in cache, check it out
var_dump($data);
}
In a text file. Oldest way of saving stuff (almost). Or do a cronjob to run the script with the function each 5 minutes independently on the visits.
Use caching, such as APC!
If the resource is really big, this may not be the best option and a file may then indeed be better.
Look at:
apc_store
apc_fetch
Good luck!
server side is PHP + zend framework.
problem:
i have huge of data appox 5000 records and no of columns are 5 in input.txt file.
i like to read all data into memory only once and send some data to the every browser request.
but if i update that input.txt file then updated data must be auto synchronized to that
memory location.
so i need to solve that problem by using memory caching technique.but caching technique
has expire time.but if input.txt is updated before cache expire then i need to auto synchronize to that memory location.
now i am using zend framework 1.10.is it possible in zend framework.
can anybody give me some line of code of zendfrmawork
i have no option to use memchached server(distributed).
Only zend framwork.
It is possible to cache something like that using zend framework.
Check Zend documentation online - its not complete but can give you a head start:
http://framework.zend.com/manual/en/zend.cache.introduction.html
Use lazy loading like this (1h cache is usually OK).
function getData() {
$cache = ...; //get your memory cache here
$cacheId = 'MyCacheId'; //cache id for your data
$loadTimeCacheId = 'dataLoadCacheId'; //cache id for data load timestamp
$cacheLength = 3600; //seconds
$data = $cache->load($cacheId);
$loadTime = (int) $cache->load($loadTimeCacheId);
if (!$data || filemtime('/path/to/your/file') > $loadTime) {
$data = ...; //real loading here
$cache->save($data, $cacheId, array(/*no tags*/), $cacheLength); //save data to cache
$cache->save(time(), $loadTimeCacheId, array(/*no tags*/), $cacheLength); //save load timestamp
}
return $data;
}
Best option is to use Zend_Cache_Frontend_File pointed to your file and Zend_Cache_Backend_Memcached. There is virtually no other option how to store anything in memory than Memcache or APC. It cannot be done without external extension IMO.