Content cache output PEAR cache
Next we start to explore more commonly used caching technologies, which is also the focus of this article. First we use the cache package in PEAR. PEAR can cache content in files, databases or memory. Let's take files as an example.
Here is a small PHP program that does not use caching:
pear_content_cache1.php
<?php
echo "This is the content. <P>";
echo "The current time is" . date('MdY H:i:s A', time()) . "<BR>";
?＞
The above program is very simple, now we add caching to it.
pear_content_cache2.php
<?php
require_once 'Cache/Output.php';
//Set the cache directory, which must be writable $cacheDir = './pear_cache';
$cache = new Cache_Output('file',array('cache_dir' => $cacheDir));
//If the nocache variable is empty, use the content in the cache //If you want to get the latest content, assign it to the nocache variable if (empty($_REQUEST['nocache']))
{
// Create a unique cache ID // Request + Cookie information $cache_id = $cache->generateID(array('url' => $_REQUEST,'post' =>$_POST,'cookies' => $HTTP_COOKIE_VARS) );
}
else
{
//If you want to get the latest content, the ID is empty $cache_id = null;
}
//Check whether the cache content corresponding to the cache ID is available if ($content = $cache->start($cache_id))
{
//The cache already exists, output directly, and end the script echo $content;
exit();
}
// The content does not exist in the cache, generate new content and write it to the cache echo "This is the content. <P>";
echo "The current time is" . date('MdY H:i:s A', time()) . "＜BR＞";
// Write the content to the cache echo $cache-＞end();
?＞
Refresh these two files respectively, and you will find that the time in the line "The current time is" in pear_content_cache1.php changes with the refresh, while this line in pear_content_cache2.php does not change. This is because pear_content_cache2.php uses caching to store the content requested by the user in a static file. When the user requests again, it is output directly from the file without the need for a program to dynamically generate the content.
For pear_content_cache2.php, if the user wants to read the latest information instead of the old information in the cache. Then you can access it with http://…/pear_content_cache2.php?nocache=1 , which will disable the caching function. Refresh it and see that the time will change accordingly.
To summarize the use of PEAR content caching class:
1. When including the PEAR package, be sure to set the correct path.
2. Contains the cache class in Output.php
require_once 'Cache/Output.php';
3. Set the cache directory
$cacheDir = './pear_cache';
confirm that this directory is writable. Cache data will be written to subdirectories of this directory.
4. Create an output cache object
$cache = new Cache_Output('file',array('cache_dir' => $cacheDir));
The first parameter indicates that we use a cache based on the "file" method, and the second parameter is a cache Array associated with directories.
5. Generate a unique cache ID
$cache_id = $cache->generateID(array('url' => $_REQUEST,'post' =>$_POST,'cookies' => $HTTP_COOKIE_VARS));
Here the generateID of the $cache object( ) method by providing an array of information (URL, HTTP POST data, and HTTP cookie) to uniquely identify this request and distinguish it from other requests.
6． Add a logical judgment statement to see if the cache data corresponding to cacheID already exists. If it exists, obtain the data and end the script.
if ($content = $cache->start($cache_id))
{
echo $content;
exit();
}
7. Place the code that generates content after the above logical statement and end using the cache object.
echo $cache->end();
function cache output PEAR cache
PEAR can not only cache the output content, but also cache the result of calling a certain function. This is a very interesting feature. If your program uses a certain function frequently and the result of the call is the same, I suggest you give it a try, especially if this function runs slowly.
Next we implement a buffered call to slowFunction(), a function that executes very slowly.
<?php
require_once 'Cache/Function.php';
$cacheDir = './pear_cache/';
$cache = new Cache_Function('file',array('cache_dir' => $cacheDir));
$arr = array('apple', 'pear', 'watermelon');
$cache->call('slowFunction', $arr);
echo '＜BR＞';
$arr = array('apple', 'pear', 'watermelon');
slowFunction($arr);
function slowFunction($arr = null)
{
echo "A function that executes very slowly: ( <br>";
echo "The current time is" . date('MdY H:i:s A', time()) . '<br>';
foreach ($arr as $fruit)
{
echo "I ate a $fruit <br>";
}
)
?＞
The following is the script execution result of the example:
a function that executes very slowly.
The current time is Jul-28-2004 17:15:57 PM
I ate an apple I ate a pear I ate a watermelon
A function that executes very slowly :(
The current time is Jul-28-2004 17:17:55 PM
I ate an apple I ate a pear I ate a watermelon
In the code, the Cache/Function.php class is used to perform the function buffering function. The $cache variable is a Cache_Function object that uses file-based function caching and is stored in the $cacheDir directory. To cache a function call, the call() method of the Cache_Function object $cache should be used like this: $cache->call('slowFunction', $arr);
Here, the slowFunction() function is called, and the parameter is an array $arr, This function is cached in a file in the $cacheDir directory. Any subsequent calls to this function will have the result of the function execution returned by $cache->call(). Function caching and usage are very similar to content caching, so I won’t go into details. Please check the PEAR manual for details.