Summary of PHP page caching methods_PHP tutorial

Summary of php page caching methods

The ob series functions are mainly used in php page caching, such as ob_start(), ob_end_flush(), ob_get_contents(), but more advanced Caching does not use these functions. An example will be given at the end of this article to illustrate.

Let’s first take a look at the ob series functions commonly used for caching:

ob_start(): The sign of the start of page cache. The content under this function is saved in the page cache until ob_end_flush() or ob_end_clean();

ob_get_contents(): used to obtain the content in the page cache. After obtaining it, we can process the content however we want, filter fields, match content, etc.~~~

ob_end_flush(): Indicates the end of page caching, and as verified by me, the cached content will be output to the current page, which means the cached content can be displayed.

Using these three PHP functions, you can achieve powerful functions. If the database query volume is large, you can use cache to solve this problem.

The following is the encoding part.

1. Initialization function, usually setting the page cache path, cache file naming format, etc., which can be customized according to personal preferences. The identification ID used here is the encrypted $_SERVER[REQUEST_URI] parameter. The last part of this function is There is an if judgment. If the cache period has not passed, load the cache file, otherwise load the source file. The code is as follows:

The code is as follows:

function page_init()
{ 
$url = $_SERVER['REQUEST_URI'];//Sub-url, this parameter is generally unique
$pageid = md5($url);
$dir = str_replace('/','_',substr($_SERVER['SCRIPT_NAME'],1,-4));
//Directory naming method, such as exp_index
If(!file_exists($pd = PAGE_PATH.$dir.'/'))@mkdir($pd,0777) or die("$pd directory creation failed");
//Such as cache/page/exp_index/
Define('PAGE_FILE',$pd.$pageid.'.html');
​ ​ //Such as cache/page/exp_index/cc8ef22b405566745ed21305dd248f0e.html
$contents = file_get_contents(PAGE_FILE);//Read out

If($contents && substr($contents, 13, 10) > time() )//corresponds to the custom header added in the page_cache() function
{
echo substr($contents, 27);
exit(0);
}  
Return true;
}

2. Page cache function. A trick is used here. Add a header information - expiration time to the content of the cache file, so each time you only need to compare the expiration time in the header with the current time. In page_init( ) function, you can determine whether the cache has expired. The code is as follows:

Copy the code The code is as follows:

function page_cache($ttl = 0)
{
$ttl = $ttl ? $ttl : PAGE_TTL;//Cache time, default 3600s
$contents = ob_get_contents();//Get content from cache
$contents = "n".$contents;
​​​ //Add custom header: expiration time = generation time + cache time
File_put_contents(PAGE_FILE, $contents);//Write to cache file
Ob_end_flush();//Release cache
}

3. When using functions, please note that these two functions are executed in sequence, and don’t forget ob_start(). The code is as follows:

The code is as follows:

Page_init();//Page cache initialization
                                                                                                                                 
...//Code segment

Page_cache(60);//usually the last line

?>

Example 2. Here is an example to illustrate PHP page caching technology. The code is as follows:

The code is as follows:

$_time =10;
$dir="D:php";

function cache_start($_time, $dir)
{
$cachefile = $dir.'/'.sha1($_SERVER['REQUEST_URI']).'.html';
$cachetime = $_time;
ob_start();
if(file_exists($cachefile) && (time()-filemtime($cachefile) < $cachetime))
{
include($cachefile);
Ob_end_flush();
exit;
}
}

function cache_end($dir)
{
$cachefile = $dir.'/'.sha1($_SERVER['REQUEST_URI']).'.html';
$fp = fopen($cachefile, 'w');
fwrite($fp, ob_get_contents());
fclose($fp);
ob_end_flush();
}

cache_start($_time, $dir);
//The following is the output content, placed between the cache_start and cache_end methods
for ($i=0;$i<5;$i++)
{
echo $i;
sleep(1);
}
cache_end($dir);
?>

For example, using generated files for caching, the code is as follows:

The code is as follows:

ob_start();
/**
* @author He Minghui
* @copyright 2009-3-13
* @param string $cache_folder cache folder
* @param int $cache_create_time file cache time
* @example $cache=new Esj_Cache('./_cache',100)
* @example $cache->read_cache() reads the cache and outputs
* @example $cache->creatre_cache() creates a cache file (put it at the end of the file)
* @example $cache->list_file() returns a list of all cache files
* @example $cache->del_file() deletes all cache files
*/

class Esj_Cache{
private $cache_folder=null;//cacher folder
private $wroot_dir=null;//site directory
private $cacher_create_time=null;//Creation time of cacher file

public function __construct($cache_foldername,$cacher_time=100)
{
ob_start();
$this->wroot_dir=$_SERVER['DOCUMENT_ROOT'];
$this->cache_folder=$cache_foldername;
$this->cacher_create_time=$cacher_time;
}

public function read_cache()
{
try {
if(self::create_folder($this->cache_folder))
{
self::get_cache();//Output cache file information
}else
{
echo "Cache folder creation failed!";
return false;
}

}catch(Exception $e){
echo $e;
return false;
}
}

//Test whether the cache folder exists
private function exist_folder($foler)
{
if(file_exists($this->wroot_dir."/".$foler)){
return true;
}else {
return false;
}
}

//Create a new folder
private function create_folder($foler)
{
if(!self::exist_folder($foler))
{
try{
mkdir($this->wroot_dir."/".$foler,0777);
chmod($this->wroot_dir."/".$foler,0777);
return true;
}catch (Exception $e)
{
self::get_cache();//Output cache
return false;
}
return false;
}
else
{
return true;
}
}

//Read cache file
private function get_cache()
{
$file_name=self::get_filename();
if (file_exists($file_name)&&((filemtime($file_name)+$this->cacher_create_time) > time()))
{
$content=file_get_contents($file_name);
if($content)
{
echo $content;
ob_end_flush();
exit;
}else
{
echo "File reading failed";
exit;

}

}
}

//Return the name of the file
private function get_filename()
{
$filename=$file_name=$this->wroot_dir.'/'.$this->cache_folder.'/'.md5($_SERVER['QUERY_STRING']).".html";
return $filename;
}

//Create cache file
public function create_cache()
{
$filename=self::get_filename();
if($filename!="")
{
try{
file_put_contents($filename,ob_get_contents());
return true;
}catch (Exception $e)
{
echo "Failed to write cache:".$e;
exit();
}
return true;
}
}

// Get all files in cache
public function list_file()
{
$path=$this->cache_folder;
if ($handle = opendir($path)) {
while (false !== ($file = readdir($handle))) {
if($file!="." && $file!="..") {
$path1=$path."/".$file;
if(file_exists($path1))
{
$result[]=$file;
}
}
}
closedir($handle);
}
return $result;
}

//Delete all files in cache
public function del_file()
{
$path=$this->cache_folder;
if ($handle = opendir($path)) {
while (false !== ($file = readdir($handle))) {
if($file!="." && $file!="..") {
$path1=$path."/".$file;
if(file_exists($path1))
{
unlink($path1);
}
}
}
closedir($handle);
}
return true;
}

}

?>

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