Question

I’ve just started a small library which will need to screen scrape from various URLs and search for specified strings. To improve performance, I want to cache the contents of the retrieved page (for the duration of the request, so in-memory).

I’ve currently got this:

class Scraper {

    private $CI;
    private $Cache;


    function __construct() {
        $this->CI =& get_instance();
        $Cache = array();
    }

    public function GetPage($Url) {
        if(!isset($Cache[$Url])) {
            dump("Retrieving");
            $Cache[$Url] =  "DATA";//file_get_contents($Url);
        }
        return $Cache[$Url];
    }

    public function FindString($Url, $String) {
        $Contents = $this->GetPage($Url);
        $Ret = (strpos(strtolower($Contents), strtolower($String)) !== false);
        return $Ret;
    }
}

NB: To improve performance while debugging, I’m just dumping “DATA” into the cache rather than fetching the page.

Now, I’ve got a loop which repeatedly calls FindString() with the same URL.

I’d expect the first call to print out “retrieving” and after that, see nothing else. In fact, I see “retrieving” repeatedly.

I suspect I’ve got a scoping issue somewhere – either the library itself isn’t a singleton so each call to FindString reaches a unique instance – or the Cache variable is being reinitialised somehow.

Can someone please suggest next steps for debugging.

(dump() just formats stuff nicely for me)

Answer 1

You are missing an $this on all places where you access the instance variable $Cache. The code should be:

class Scraper {

    private $CI;
    private $Cache;


    function __construct() {
        $this->CI =& get_instance();
        $this->Cache = array();
    }

    public function GetPage($Url) {
        if(!isset($this->Cache[$Url])) {
            dump("Retrieving");
            $this->ache[$Url] =  "DATA";//file_get_contents($Url);
        }
        return $this->Cache[$Url];
    }

    public function FindString($Url, $String) {
        $Contents = $this->GetPage($Url);
        $Ret = (strpos(strtolower($Contents), strtolower($String)) !== false);
        return $Ret;
    }
}