**Opencart**: v.1.5.6.4

When someone searches for "*iphone nikon*" in Opencart's search input text field the results are:  

"*There is no product that matches the search criteria.*" (example - <https://o-v156x.my-soul.net/index.php?route=product/search&search=iphone%20nikon>)

What I want to achieve is to change the search query from **AND** to **OR** to get results: 

* iphone
* Nikon D300

or all the products where these words appear in **product's name**.

I am not interested in live search (auto-complete or auto-suggest or auto-correct).

I am pretty sure that the changes I want to make (by using vQmod) are inside the file `/catalog/model/catalog/product.php`.  

Where exactly is the code needed to be changed?