Can I use WordPress with OpenCart?
This really depends on the level of integration you want between OpenCart and WordPress.
First, make sure you actually need this. WordPress and OpenCart are different systems meant for different purposes and it’s not always the best idea to try and combine them.
If your main business is e-commerce and you need WordPress for things like blogging, you may want to consider getting one of OpenCart blog extensions instead.
On the other hand, if most of your business is covered by WordPress and you only need OpenCart to sell a few products, consider using a WordPress e-commerce plugin instead (anything popular such as Easy Digital Downloads or WooCommerce).
The reason is that you’ll be much better off with specific tools that are designed to be used together rather than trying to combine two different systems.
If you decide to proceed, there are two different ways.
First, you can always install them side by side and use similar design for both WordPress and OpenCart. This is the easiest way, but it will also mean your WordPress users will need to apply for a separate account to purchase products in your OpenCart store and you will not be able to easily share content between WordPress and OpenCart.
Alternatively, you can use one of the WordPress + OpenCart integration plugins that are available out there. Some of the bigger ones are WooCart by SoftPHP and OCWP by iSenseLabs. This will give you a bit more integration and make some additional things possible such as displaying OpenCart content in WP and vice versa.
However, no matter which way you decide to take, make sure you have someone with OpenCart and WordPress development knowledge to help you with this.