thumbnail with cache

function render( $image, $params ) {
        //Set defaults
        $path = '';
        $width = 150;
        $height = 225;
        $quality = 75;
        $extension = 'jpg';
        //Extract Parameters
        if( isset( $params[ 'path' ] ) ) {
            $path = $params[ 'path' ] . DS;
        }
        if( isset( $params[ 'width' ] ) ) {
            $width = $params[ 'width' ];
        }
        if( isset( $params[ 'height' ] ) ) {
            $height = $params[ 'height' ];
        }
        if( isset( $params[ 'quality' ] ) ) {
            $quality = $params[ 'quality' ];
        }
        if( isset( $params[ 'extension' ] ) ) {
            $extension = $params[ 'extension' ];
        }
        //import phpThumb class with CakePHP
        App::import( 'Vendor', 'phpthumb', array( 'file' => 'phpThumb' . DS . 'phpthumb.class.php' ) );
        $thumbNail = new phpthumb;
    //WWW_ROOT and DS are CakePHP global for web root folder and Directory Seperator
        $thumbNail->src = WWW_ROOT . 'img' . DS . $path . $image;
        $thumbNail->w = $width;
        $thumbNail->h = $height;
        $thumbNail->q = $quality;
        $thumbNail->config_imagemagick_path = '/usr/bin/convert';
        $thumbNail->config_prefer_imagemagick = false;
        $thumbNail->config_output_format = $extension;
        $thumbNail->config_error_die_on_error = true;
        $thumbNail->config_document_root = '';
    //APP is a CakePHP global for the APP folder
        $thumbNail->config_temp_directory = APP . 'tmp';
        $thumbNail->config_cache_directory = WWW_ROOT . 'img' . DS . 'thumbs' . DS;
        $thumbNail->config_cache_disable_warning = true;
        $cacheFilename = $image;
        $thumbNail->cache_filename = $thumbNail->config_cache_directory . $cacheFilename;

        if( !is_file( $thumbNail->cache_filename ) ) {
            if( $thumbNail->GenerateThumbnail() ) {
                $thumbNail->RenderToFile( $thumbNail->cache_filename );
            }
        }

        if( is_file( $thumbNail->cache_filename ) ) {
    //File is a CakePHP Class that help manipulating files, I use it here to get the "last change date"
            $fullSizedImage = new File( $thumbNail->src );
            $thumbNailImage = new File( $thumbNail->cache_filename );
            //update thumbnail if original one has been updated
            if( $fullSizedImage->lastChange() > $thumbNailImage->lastChange() ) {
                if( $thumbNail->GenerateThumbnail() ) {
                    $thumbNail->RenderToFile( $thumbNail->cache_filename );
                }
            }
            return $cacheFilename;
        }

    }