Question

I am using cakephp 1.3 and I have textarea where users submit articles. On submit, I want to look into the article for certain key words and and add respective tags to the article.

I was thinking of preg_match, But preg_match pattern has to be string. So I would have to loop through an array(big).

Is there a easier way to plug in the keywords array for the pattern.

I appreciate all your help.

Thanks.

Answer 1

I suggest treating your array of keywords like a hash table. Lowercase the article text, explode by spaces, then loop through each word of the exploded array. If the word exists in your hash table, push it to a new array while keeping track of the number of times it’s been seen.

I ran a quick benchmark comparing regex to hash tables in this scenario. To run it with regex 1000 times, it took 17 seconds. To run it with a hash table 1000 times, it took 0.4 seconds. It should be an O(n+m) process.

$keywords = array("computer", "dog", "sandwich");
$article = "This is a test using your computer when your dog is being a dog";
$arr = explode(" ", strtolower($article));
$tracker = array();

foreach($arr as $word){
    if(in_array($word, $keywords)){
        if(isset($tracker[$word]))
            $tracker[$word]++;
        else 
            $tracker[$word] = 1;
    }
}

The $tracker array would output: “computer” => 1, “dog” => 2. You can then do the process to decide what tags to use. Or if you don’t care about the number of times the keyword appears, you can skip the tracker part and add the tags as the keywords appear.

EDIT: The keyword array may need to be an inverted index array to ensure the fastest lookup. I am not sure how in_array() works, but if it searches, then this isn’t as fast as it should be. An inverted index array would look like

array("computer" => 1, "dog" => 1, "sandwich" => 1); // "1" can be any value

Then you would do isset($keywords[$word]) to check if the word matches a keyword, instead of in_array(), which should give you O(1). Someone else may be able to clarify this for me though.