No talking . Just examples

class Foo
{

    private static $_bar = null;

    private function getBar()
    {
        if ( null == self::$_bar) {
            //very expensive operation
            self::$bar = $this->expensiveOperation();
        }

        return self::$bar;
    }

    private function expensiveOperation()
    {
        return 1+1;//wow
    }
}

Extending the example

class Foo
{

    private function getBar()
    {
        if ( !this->isCached()) {
            //very expensive operation
            $this->saveCache($this->expensiveOperation);
        }

        return $this->getCache();
    }

    protected function saveCache($value)
    {
        file_put_contents($this->getCachePath(),$value);
    }

    protected function getCache()
    {
        return file_get_contents($this->getCachePath());
    }

    protected function isCached()
    {
        return is_file($this->getCachePath());
    }

    private function getCachePath()
    {
        return '/path/to/somefile.txt';
    }
    private function expensiveOperation()
    {
        return 1+1;//wow
    }
}
Final example
class Cache
{
    public static function isCached($tag)
    {
        return is_file(self::isFile(self::getCacheFile($tag)));
    }

    public static function save($value , $tag)
    {

        $file = self::getCacheFile($tag);
        file_put_contents($file , $value);
    }

    public static function load( $tag)
    {
        $file = self::getCacheFile($tag);
        return file_get_contents($file);
    }

    private static function getCachePath($tag)
    {
        return "/path/to/somefile_$tag.txt";
    }
}

class Foo
{
    public static function getBar()
    {
       if ( !Cache::isCached('my_tag')) {
            //very expensive operation
            Cache::save($this->expensiveOperation(),'my_tag');
        }
        return $this->load('my_tag');
    }

    private function expensiveOperation()
    {
        return 1+1;//wow
    }
}

All three examples are variations of the same technique.
Of course , the  file_get_contents thing is used for the example's sake only

1. EllisGL Says:
   November 10th, 2009 at 10:39 pm

   I just use JG_Cache =)

2. khelo Says:
   November 11th, 2009 at 12:21 am

   Thank you for your comment. I generally use Zend_Cache.

   My post is just a simple example on how caching can be used ,on different contexts, or how it can evolve from something simple.

   JG_Cache illustrates the third situation very well.

3. bip Says:
   November 11th, 2009 at 2:43 am

   Very useful examples. Simple, yet powerful.

4. Webuml – Developer Notes » Blog Archive » Using a decorator for caching purposes Says:
   November 18th, 2009 at 4:12 pm

   [...] my previous post I  gave some examples on  how caching can evolve.   However , what annoys  me in the  [...]