Hi dear, the search of ps 1.7.4 is still as bad as you find in 1.7.3,1.7.2 , completely unusable. Your search.php can work on 1.7.4? The goal is simply to use a AND LOGIC instead OR in the query result.
If you have server when can install package you must consider install elastich searche module. I use that and it work GREAT.
I've found another trick to tune up 1.7.4 search. The big problem on the defaul class is that it use an OR operator,so you get lot of result but also you get higher rank on products that has duplicated word in their field. Using or instead and your result don't match the query you are searching. If you try to find "Z H" you will have a higher result for entry with
"Z Z Z"
than one with
"Z H A"
And this is Creasy. To mitigate this function we have installed a module "auto keyword generator" and we configure it for generate tags from short desc. The module REMOVE duplicate entry and we teach search to use title and tags instead short desc . In title is hard to find duplicated words, instead in short desc it can happen frequently.