Weighting applies more to sorting than searching.
PHP doesn't provide a direct method of weighting search results but that doesn't stop you from writing your own. You want to create a result array that looks like this:
array (..) [
{record_id} => {weight},
{record_id} => {weight},
....
]
and populate using a search algorithm which multiplies the number of matches in 'title' by 2 and in the other fields by 1 for the weight values. Then sort it by weight.
Richard.