php缓存----磁盘缓存

PHP开发也有几个月了，感觉php缓存是很重要的一块，无论是页面级的（主要指smarty)还是dao级的。使用上还不怎么熟，但还是记录下笔记。本篇讲述的缓存是写到磁盘文件，这是看piwik源码时看到的，感觉思想很好，这也得益于PHP的var_export 方法。主要把要保存的内容（int,string,也可以使array)保存为php文件，这样当include这个php文件后，保存的内容就自动当做变量被include进来了。

 

源码如下：

<?php
class Piwik_CacheFile
{
    protected $cachePath;
    protected $cachePrefix;
    
    function __construct($directory)
    {
    	$this->cachePath = PIWIK_USER_PATH . '/tmp/cache/' . $directory . '/';
    }
    
	function get($id) 
	{
	    $cache_complete = false;
	    $content = '';
	
	    // We are assuming that most of the time cache will exists
	    $ok = @include($this->cachePath . $id . '.php');
	
	    if ($ok && $cache_complete == true) {
	        return $content;
	    }

	    return false;
	}
	
	function set($id, $content)
	{
		if( !is_dir($this->cachePath))
		{
			Piwik_Common::mkdir($this->cachePath);
		}
	    if (!is_writable($this->cachePath)) {
	        return false;
	    }
	
	    $id = $this->cachePath . $id . '.php';
	
	    $cache_literal  = "<"."?php\n\n";
	    $cache_literal .= "$"."content   = ".var_export($content, true).";\n\n";
	    $cache_literal .= "$"."cache_complete   = true;\n\n";
	    $cache_literal .= "?".">";
	
	    // Write cache to a temp file, then rename it, overwritng the old cache
	    // On *nix systems this should guarantee atomicity
	    $tmp_filename = tempnam($this->cachePath, 'tmp_');
	    if ($fp = @fopen($tmp_filename, 'wb')) {
	        @fwrite ($fp, $cache_literal, strlen($cache_literal));
	        @fclose ($fp);
	
	        if (!@rename($tmp_filename, $id)) {
	            // On some systems rename() doesn't overwrite destination
	            @unlink($id);
	            if (!@rename($tmp_filename, $id)) {
	                // Make sure that no temporary file is left over
	                // if the destination is not writable
	                @unlink($tmp_filename);
	            }
	        }
	        return true;
	    }
	    return false;
	}

    function delete($id)
    {
        $filename = $this->cachePath . $id . '.php';
        if (file_exists($filename)) {
            @unlink ($filename);
            return true;
        }
        return false;
    }
}