Counting keywords in database record

Hi all, I'm designing a site that is powered by a database, with three main fields, called "name", "details, and "description". Users enter their search term in a field on the search page, and then my PHP script selects all rows from the DB where that keyword appears in any of the fields. I'd like to be able to count the number of times the keyword appears in each row, and then sort the search results by relevance. What is going to be the most efficient way of doing this? Currently, I'm thinking I'll do this... Select all the rows from the database Copy the three fields from each row into an array Count the number of times the keywords appear in each row, and insert this number into a column in the array Sort the array by the "keyword count" column Loop through the array to display results This seems like a horribly inefficient way of doing this, but it's the only way I've been able to come up with. Is there a better way? Can I use a regular expression to count the number of times the keyword appears in each row? Or will the count_chars function work on words? Thanks in advance, Stewart