Writing Your Own Template Caching Class In PHP

Writing Your Own Template Caching Class In PHP - The Code Explained (contd.)
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if (is_file($filename)) {
clearstatcache();

if (filemtime($filename) > (time() - $this->_cacheLifetime)) {
$isCached = true;
}
}

The first "if" construct simply checks if the file exists. The second if construct checks if the time since the file was last modified is greater than $_cacheLifetime. Let's move on to the _addCache() method. This method simply creates a cache file:

function _addCache($content, $file, $id = false)
{
$id = $id ? md5($id . basename($file)) : md5(basename($file));
$filename = $this->_cacheDir . '/' . $id . '/' . basename($file);
$directory = $this->_cacheDir . '/' . $id;

@mkdir($directory, 0775);

if ($fp = fopen($filename, 'wb')) {
fwrite($fp, $content);
fclose($fp);
}
}

As you can see, this code snippet is pretty similar to the code in the isCached() method.

@mkdir($directory, 0775);

The above function call simply creates the directory for the cache item.

if ($fp = fopen($filename, 'wb')) {
fwrite($fp, $content);
fclose($fp);
}

This code opens a stream to the cache file (which is created there and then), and writes everything inside $content to the file. There's actually only one method left before the class is finished. The last method we'll add is _getCache(). This method is used for retrieving the content of a cache file:

function _getCache($file, $id = false)
{
$id = $id ? md5($id . basename($file)) : md5(basename($file));
$filename = $this->_cacheDir . '/' . $id . '/' . basename($file);

if ($fp = fopen($filename, 'rb')) {
$content = fread($fp, filesize($filename));
fclose($fp);
}

return isset($content) ? $content : false;
}

Here's the only differing part from the last function:

if ($fp = fopen($filename, 'rb')) {
$content = fread($fp, filesize($filename));
fclose($fp);
}

return isset($content) ? $content : false;

This code simply opens a stream to the cache fil, and reads it all into a variable. The variable is then returned. That's it! The class is now finished.

The Whole Class
Here's the whole class in one part. Just in case you're in a hurry:

<?php

class Template {

var $_variables = array();
var $_caching = false;
var $_cacheDir = '/cache';
var $_cacheLifetime = 120;

function addVar($name, $value)
{
$variables = &$this->_variables;
$variables[$name] = $value;
}

function display($file, $id = false)
{
echo $this->fetch($file, $id);
}

function fetch($file, $id = false)
{
if ($this->_caching == true && $this->isCached($file, $id)) {
$output = $this->_getCache($file, $id);
} else {
$output = $this->_getOutput($file);

if ($this->_caching == true) {
$this->_addCache($output, $file, $id);
}
}

return isset($output) ? $output : false;
}

function _getOutput($file)
{
extract($this->_variables);
$file = realpath($file);

if (file_exists($file)) {
ob_start();
include($file);
$output = ob_get_contents();
ob_end_clean();
} else {
trigger_error("Failed opening the template file '$file'. The file doesn't exist.", E_USER_ERROR);
}

return !empty($output) ? $output : false;
}

function setCacheDir($dir)
{
$dir = realpath($dir);

if (is_dir($dir) && is_writable($dir)) {
$this->_cacheDir = $dir;
} else {
trigger_error("The cache directory '$dir' either doesn't exist, or it cannot be written to by PHP", E_USER_WARNING);
$this->_cacheDir = '';
$this->_caching = false;
}
}

function setCacheLifetime($seconds)
{
if (is_numeric($seconds)) {
$this->_cacheLifetime = $seconds;
}
}

function setCaching($state)
{
if (is_bool($state)) {
$this->_caching = $state;
}
}

function isCached($file, $id = false)
{
$id = $id ? md5($id . basename($file)) : md5(basename($file));
$filename = $this->_cacheDir . '/' . $id . '/' . basename($file);

if (is_file($filename)) {
clearstatcache();

if (filemtime($filename) > (time() - $this->_cacheLifetime)) {
$isCached = true;
}
}

return isset($isCached) ? true : false;
}

function _addCache($content, $file, $id = false)
{
$id = $id ? md5($id . basename($file)) : md5(basename($file));
$filename = $this->_cacheDir . '/' . $id . '/' . basename($file);
$directory = $this->_cacheDir . '/' . $id;

@mkdir($directory, 0775);

if ($fp = fopen($filename, 'wb')) {
fwrite($fp, $content);
fclose($fp);
}
}

function _getCache($file, $id = false)
{
$id = $id ? md5($id . basename($file)) : md5(basename($file));
$filename = $this->_cacheDir . '/' . $id . '/' . basename($file);

if ($fp = fopen($filename, 'rb')) {
$content = fread($fp, filesize($filename));
fclose($fp);
}

return isset($content) ? $content : false;
}
}

?>

I'll now show you a few examples on advanced usage of this class in real-world PHP applications.
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