String substitution using UUIDs

Hey folks,

this is post #2 of my 30 day challenge. If you've ever written any non-trivial String processing code, you've probably ran into the situation where you wanted to exclude certain parts of your string for a certain operation. Usually that would mean you have to tokenize your string, or adjust the operation you want to run so it doesn't affect the part of the string you want to exclude from it. Both of those solutions can be fairly time intensive so I was looking for a shortcut and found one.

Let me make a practical example so this sounds less like hypothetical BS: Let's say you have written your own Textile-inspired parser, but you want to allow sections to remain untouched by the parser as well. My solution: Just substitute the parts you want to exclude from textile processing with UUIDs and put them back in afterwards:

class Common{
static function substitue($regex, $text) {
preg_match_all($regex, $text, $matches);
if (empty($matches[0])) {
return array($text, array(), array());
}
$r = array();
foreach ($matches[0] as $match) {
$uuid = String::uuid();
$r[1][] = $uuid;
$r[2][] = $match;
$text = r($match, $uuid, $text);
}
$r[0] = $text;
return $r;
}
}

$html = 'This *is* my sample [literal]text for *this* post[/literal]!';
list($html, $uuids, $values) = Common::substitute('/\[literal\].+\[\/literal]/sU');
// $html is now: 'This *is* my sample 8ad0fe9-ec3c-4b0d-b314-7a111030b5da!';
$html = Textile::parse($html);
// $html is now: 'This <strong>is</strong> my sample 8ad0fe9-ec3c-4b0d-b314-7a111030b5da!';
$html = str_replace($uuids, $values, $html);
// $html is now: 'This <strong>is</strong> my sample [literal]text for *this* post[/literal]!';

I actually found having this little substitution method useful a few times in the past so I thought I share it ; ). Suggestions for improvements and other approaches are more then welcome!

-- Felix Geisendörfer aka the_undefined

PS: I have decided to allow myself to write my posts for the weekend the night before and have them auto-published. Otherwise my girlfriend is going to kill me ; ).

&nsbp;

String substitution using UUIDs

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