position: relative

Here’s a very simple and generic data cache class for Codeigniter:

• since the end of 2008 renames are atomic on both Windows and Linux
• I use the filemtime with the ttl, this means no extra expiry file
• the getter doesn’t return the data, but stores it in a buffer
• values are stored as serialized php files in the CI cache directory
• use it as a plugin: $CI-<load-<plugin(‘SerCache’); //I didn’t want it to behave like a library

Hope someone finds it useful. A more advanced cache for CI may be found here and another one here.

class SerCache {
    public  $filename;
    private $tempfile;
    private $ttl;
    private $default_ext = '.ser';
    public  $buffer;
    
    /**
     * Simple data cache
     * @param string name   filename of the cache file (probably an md5 hash)
     * @param mixed ttl time to live in seconds; -1 circumvents caching, 'forever' is infinite
     */
    public function __construct($name, $ttl = 'forever')
    {
        $CI =& get_instance();
        $path = $CI->config->item('cache_path');
        $this->cache_dir = ($path == '') ? BASEPATH.'cache/' : $path;
        
        $this->ttl = $ttl;
        if ($ttl == -1)
            return FALSE;
        $this->filename = $this->cache_dir.$name.$this->default_ext;
        $this->tempfile = $name.getmypid();
    }
    
    /** 
     * Fetch data into $this->buffer
     * @return bool FALSE if expired or not set, TRUE otherwise 
     */ 
    public function get()
    {
        if ($this->ttl == -1)
            return FALSE;
        if ($this->ttl == 'forever')
        {
            if (!file_exists($this->filename))
                return FALSE;
        }
        else
        {
            if ((!file_exists($this->filename)) OR (filemtime($this->filename) + $this->ttl < time()))
                return FALSE;
        }
        $this->buffer = unserialize(file_get_contents($this->filename));
        return TRUE;
    }
    
    /**
     * Save serialized value to file
     * @param mixed value value to be serialized
     */
    public function put($value) {
        if ($this->ttl == -1)
            return FALSE;
        file_put_contents($this->tempfile, serialize($value));
        rename($this->tempfile, $this->filename);
    }
    
    /**
     * Deletes the cachefile
     */
    public function destroy() {
        if (file_exists($this->filename))
        {
            unlink($this->filename);
        }
    }
    
    /**
     * Returns the filemtime of the cache file
     */
    public function filemtime() {
        if (file_exists($this->filename))
            return filemtime($this->filename);
        return 0;
    }
}

Example:

$cache = new SerCache('something', $cacheTTL);
if ($cache->get()) {
$var = $cache->buffer;
} else {
//create var here...
$cache->put($var);
}