I have a customized version of Magento 1.7 community edition. I want to upgrade it to 1.9.x. What are the major changes done in 1.9.x which I need to be careful of during the upgradation ?
Fallow below steps during upgrade:
• Community app/code/community
• Local app/code/local
• your theme or package (app/design/frontend/default/<your theme> or app/design/frontend/<your package>)
• custom folders from Skin (both for adminhtml and frontend).
• copy your custom xml files from app/etc/modules/ to current app/etc/modules/
• any custom admin theme folder from adminhtml/default/yourtheme.
• copy your custom folders from adminhtml/default/default/ (1.7) to adminhtml/default/default/(1.9).
• custom js files if any from app/js/.
Please accept my solution if you satisfied.
There's actually number of things changed. For example few more forms have form_key added and there's a new block whitelisting feature. The list doesn't end there, but it's nothing too complicated as long as no changes have been made to your store core. v1.7 is the oldest version that can be upgrade to latest one relatively painlessly.
The most important upgrade of Magento 1.9 is that now it takes less time and less spending to code your site for mobiles and tablets, because Magento 1.9 supports responsiveness at core. Magento 1.9 support PHP 5.4 and Zend Framework 1.12.3. Don't miss to upgrade magento from 1.7 to 1.9. You can try Magento to Magento migration tool of Lit-extension as a choice to upgrade magento automatically.
Magento 1.9 doesn't still support PHP 5.6 / PHP 7.x though. Without fixes the first one will throw warning (saturates system.log) and the the last one will fail outright. Since older PHP versions are deprecated by now, you're in tough position one way or another as majority of ISP-s doesn't officially support them anymore.