At each step, if the search string is found, the user has put in one of those special
SQL keywords that doesn’t return rows, so the variable $return_rows is set to false,
different from its original value, true.
Finally, at the end of this curly-brace love fest, the if statements unwind back to the
main program, and either $returns_rows has a value of true because none of the
searches matched, or false because one of them did.