Question

I have this web page where users can add smilies to their comments. And I want to limit the number of smilies per comment. The “system” works but I have some problems with the regex part.
I have my smilies defined in a config file like so:

$config['Smilies'] = Array (
    // irrelevant stuff
    'smilies' => Array (
        ':)' => 'smile.gif',
        ':(' => 'sad.gif',
        // some more smilies
        's:10' => 'worship.gif',
        's:11' => 'zip.gif',
        's:12' => 'heart.gif',
        // some more smilies
        's:1' => 'dry.gif',
        's:2' => 'lol.gif',
        's:3' => 'lollol.gif',
        // some more smilies
    )
);

And then when I validate the comment (to see how many smilies are there), I loop trough this array and match the smile to the content of the comment. The regex is used like this:

foreach ( $this->config['smilies'] as $smilie => $smilieImage )
{
    $matches = Array ();
    Preg_Match_All ( '/' . Preg_Quote ( $smilie ) . '/i', $Content, $matches );

    $numOfFoundSmilies += Count ( $matches[0] );
}

The problem is that the if I enter “s:10” into the comment, the above code will find two matches: “s:10” and “s:1”. My knowledge of regular expressions is very poor, and I can’t figure this one out.

Answer 1

Regular expressions are greedy by default (at least PCREs). Usually you could circumvent this:

/a+/ # selects the whiole string from "aaaaaaa"

/a+?/ # selects only "a"

In your case, this doesn’t help much, since you can’t just throw in a question mark somewhere. The only possibility is to re-order your search array and instantly replace the found places. Search first for s:10 and second for s:1, and use preg_replace() instead of the matching. This way, the second doesn’t find the first anymore.

Another possibility: Split your search array in two. If you know, that the one always has the structure ‘s:’ plus digits, you could have your regexp in this second loop like

Preg_Match_All ( '/' . Preg_Quote ( $smilie ) . '(?![0-9])/i', $Content, $matches );

with (?![0-9]) a look ahead expression looking for any non-digit.

And a third one: If you allow (== convert) smileys only at certain places, you could use this:

Preg_Match_All ( '/\b' . Preg_Quote ( $smilie ) . '\b/i', $Content, $matches );

\b is a “word boundary”, usually any not-(letter, digit, underscore). Drawback is obviously, that not all smileys (like “abc;-)xyz”) will be found.