Get data faster from databasse
What you have is a full table scan with no way to speed it up.

Look into FULLTEXT(bussiness_name, trading_name) indexing as a much faster way to search for words.  You would need MATCH (bussiness_name, trading_name) AGAINST("$data['searchstring']" IN BOOLEAN MODE).

If status is rarely 1 and is_approved is rarely 1, then this would help: INDEX(status, is_approved).

You should also protect yourself from SQL injection by escaping the searchstring.