there is just one ‘index.php’ and that generate all the contents with different titles, meta descriptions…i mean each page is whole new page but created from similar part of URL ‘my_domain.com/index.php?’
with mod_rewrite, i will have seemingly SEO friendly URL
First, will re-writing dynamic URLs to static URLs help your SEO? The answer is - very little, if at all. Search engines are perfectly happy crawling and indexing dynamic pages. If your page is essentially static, they would prefer you to use a static URL, but it isn’t a problem if you don’t.
Second, will re-writing dynamic URLs to static URLs help your usability? In theory, yes it will … but not the way you’ve done it! The benefits of static URLs is that they are easy to type in than multivariate queries (being shorter and having less scope for error with no ?s and &s), and that if you have a hierarchical structure, it is easy to go up a level - you can just delete the last part of the URL, without worrying about the site’s internal navigation.
But what happens if a user tries that on your site - my_domain.com/chapter/1/page/ You should never have a ‘folder’ that maps to a query name - either do without the query name altogether and have my_domain.com/1/10 or combine the query name and term into one, like my_domain.com/chap1/page10.
The fact that you have unique URLs is good. Search-friendly URLs as you describe can make a difference however only if they include the keywords of the content of the page. Depending on how long your pages have been indexed for, you’d want to ensure that you redirect from the old URLs to the new URLs.
From my experience, it wouldn’t be one of the priorities on my list to fix that based on what you’re saying, and I would probably focus more on attracting links, and ensuring that content, titles and meta descriptions are written to target what people are searching for more precisely.