php match string to multiple array of keywords

Question

I'm writing a basic categorization tool that will take a title and then compare it to an array of keywords. Example:

$cat['dining'] = array('food','restaurant','brunch','meal','cand(y|ies)');
$cat['services'] = array('service','cleaners','framing','printing');
$string = 'Dinner at seafood restaurant';

Are there creative ways to loop through these categories or to see which category has the most matches? Note that in the 'dining' array, I have regex to match variations on the word candy. I tried the following, but with these category lists getting pretty long, I'm wondering if this is the best way:

$keywordRegex = implode("|",$cat['dining']); 
preg_match_all("/(\b{$keywordRegex}\b)/i",$string,$matches]);

Thanks, Steve

EDIT: Thanks to @jmathai, I was able to add ranking:

    $matches = array(); 
    foreach($keywords as $k => $v) {
        str_replace($v, '#####', $masterString,$count);
        if($count > 0){
            $matches[$k] = $count;
        }
    }
    arsort($matches);

Answer 1

This can be done with a single loop.

I would split candy and candies into separate entries for efficiency. A clever trick would be to replace matches with some token. Let's use 10 #'s.

$cat['dining'] = array('food','restaurant','brunch','meal','candy','candies');
$cat['services'] = array('service','cleaners','framing','printing');
$string = 'Dinner at seafood restaurant';

$max = array(null, 0); // category, occurences
foreach($cat as $k => $v) {
  $replaced = str_replace($v, '##########', $string);
  preg_match_all('/##########/i', $replaced, $matches);
  if(count($matches[0]) > $max[1]) {
    $max[0] = $k;
    $max[1] = count($matches[0]);
  }
}

echo "Category {$max[0]} has the most ({$max[1]}) matches.\n";

Answer 2

$cat['dining'] = array('food','restaurant','brunch','meal');
$cat['services'] = array('service','cleaners','framing','printing');
$string = 'Dinner at seafood restaurant';

$string = explode(' ',$string);
foreach ($cat as $key => $val) {
  $kwdMatches[$key] = count(array_intersect($string,$val));
}
arsort($kwdMatches);

echo "<pre>";
print_r($kwdMatches);