Running preg_replace on html code taking too long - php

Question

At the risk of getting redirected to this answer (yes, I read it and spent the last 5 minutes laughing out loud at it), allow me to explain this issue, which is just one in a list of many.
My employer asked me to review a site written in PHP, using Smarty for templates and MySQL as the DBMS. It's currently running very slowly, taking up to 2 minutes (with a entirely white screen through it all, no less) to load completely.
Profiling the code with xdebug, I found a single preg_replace call that takes around 30 seconds to complete, which currently goes through all the HTML code and replaces each URL found to its SEO-friendly version. The moment it completes, it outputs all of the code to the browser. (As I said before, that's not the only issue -the code is rather old, and it shows-, but I'll focus on it for this question.)
Digging further into the code, I found that it currently looks through 1702 patterns with each appropriate match (both matches and replacements in equally-sized arrays), which would certainly account for the time it takes.
Code goes like this:
//This is just a call to a MySQL query which gets the relevant SEO-friendly URLs:
$seourls_data = $oSeoShared->getSeourls();
$url_masks = array();
$seourls = array();
foreach ($seourls_data as $seourl_data)
{
if ($seourl_data["url"])
{
$url_masks[] = "/([\"'\>\s]{1})".$site.str_replace("/", "\/", $seourl_data["url"])."([\#|\"'\s]{1})/";
$seourls[] = "$1".MAINSITE_URL.$seourl_data["seourl"]."$2";
}
}
//After filling both $url_masks and $seourls arrays, then the HTML is parsed:
$html_seo = preg_replace($url_masks, $seourls, $html);
//After it completes, $html_seo is simply echo'ed to the browser.
Now, I know the obvious answer to the problem is: don't parse HTML with a regexp. But then, how to solve this particular issue? My first attempt would probably be:
Load the (hopefully, well-formed) HTML into a DOMDocument, and then get each href attribute in each a tag, like so.
Go through each node, replacing the URL found for its appropriate match (which would probably mean using the previous regexps anyway, but on a much-reduced-size string)
???
Profit?
but I think it's most likely not the right way to solve the issue.
Any ideas or suggestions?
Thanks.

Answer 1

As your goal is to be SEO-friendly, using canonical tag in the target pages would tell the search engines to use your SEO-friendly urls, so you don't need to replace them in your code...

Answer 2

Oops ,That's really tough, bad strategy from the beginning , any way that's not your fault,
i have 2 suggestion:-
1-create a caching technique by smarty so , first HTML still generated in 2 min >
second HTMl just get from a static resource .
2- Don't Do what have to be done earlier later , so fix the system ,create a database migration that store the SEO url in a good format or generate it using titles or what ever, on my system i generate SEO links in this format ..
www.whatever.com/jobs/722/drupal-php-developer
where i use 722 as Id by parsing the url to get the right page content and (drupal-php-developer) is the title of the post or what ever
3 - ( which is not a suggestion) tell your client that project is not well engineered (if you truly believe so ) and need a re structure to boost performance .
run