As posted by Lodder, It is really hard to migrate Joomla 1.5 site to other framework. You would surely need enough months to accomplish this task.
I rather suggest you to go from Joomla 1.5 to Joomla 3.x. The migration from Joomla! 1.5 to 3.x is a major migration. There are many changes in features and database tables between these two version. It is NOT a one-click update. You will be building/installing a fresh Joomla! 3 installation and then migrating (moving) your data into it. If you haven't already, you may want to start with the Self Assessment and Planning documents.
Following are few steps:
Prepare a Location for Joomla 3
Make sure your server environment meets the technical specifications for Joomla! 3 before proceeding.
Create a new database and new user for your Joomla! 3.x site. Document the database name, database username and database password as you’ll need it when you install Joomla 3
Use Third Party Extension (Migration Tool)
I used SP Upgrade It's great tool and transfers all database flawlessly. They have good documentation too. However, it's your choice.
- Migrate all core data you want to move to Joomla 3.x. If your
migration tool asks to move Sections and Categories, definitely do
both. The conversion will happen to categories and nested categories
- Run the Database Fix by going to Extension Manager →
Database and click the Fix button in the top toolbar.
- Install your
new template or converted template so that you can see your content.
See more about Template Considerations.
- Add new menus if the tool
you chose to use didn’t bring over menus. If you want to use split
menus, set that up now.
- Add modules if the tool you chose to use didn’t bring over modules. If the tool you chose to use did bring over modules, change the module positions to the positions in your new template if required so that your modules show up and you can see what you’re working with.
- Check for duplicate alias issues and fix them
- Check your internal links. If any are broken, fix them
- Take a backup
- Install other third-party extensions and configure them (like editors, Akeeba backup, slideshows, or plugins).
- Take a backup
- If you have large extensions with data to migrate, do each one according to the developer documentation and then take a backup after each one
- If your migration tool didn’t move the images, you will want to move your images from the 1.5 site to the 3.x site. Note: keep the /stories directory unless you want to relink all your images. You can start a new organisational structure in the /images directory from here forward if stories is a mess
- If you are going to add anything to your site or use new core features like Tags, get them set up and configured at this time
- Check your URLs on the Joomla 3 site and compare to the Joomla 1.5 site. If they are different, document each (an excel spreadsheet is helpful) 1.5 URL and what Joomla 3.x URL they will be going to so that you can do redirects and keep your ranking
- Take a backup. Clean up more. Test everything. Take a backup.
- Move or change or add updated data from the 1.5 site to the Joomla 3 site
- Host it on your hosting space. Make sure you have taken backup at all intervals so that if something goes wrong, you have previous version ready.
Joomla 3.x is way better than Joomla 1.5 in every aspect. I encourage
you to play with it on demo site. End user will never regret to have
this awesome CMS.