searchParser: Class to parse search term strings.
version 0.5.0

Marty Vance
15 Oct 2010

License: GNU GPL v2: http://www.gnu.org/licenses/old-licenses/gpl-2.0.html

This is a search string parser I started writing because I couldn't find one
with the features I wanted.  It's not complete yet: see TODO below.

Features:
Support for unary operators (+/-).  Plus is always assumed if - is not
present.

Localized support for boolean operators (AND/OR).

Support for field identifiers (title:foo).

Localized support for quote and apostrophe characters.

Constructor args:
$q: array of quote characters
$a: array of apostrophe characters
$n: array of boolean AND operator strings
$o: array of boolean OR operator strings

Public methods:
__get($name): returns the value of a member variable

setString($string): takes a string as an arg.  Returns bool true if the
arg is a string of > 0 length after parsing it, or returns false.

dumpPhrases(): returns a formatted string of the elements found in the
previously given search string.

getWhere($fields): takes an array of database field identifiers and returns
an SQL where clause suitable for use in queries.

TODO:
- Finish private function construct(): this is where the flat list of
pieces assembled in parse() get nested into a structure more representavive
of the user's intent.
- Error/exception handling.
- Support for unmatched (left/right) quote characters.
- Default constructor arg values suitable for English (?).
- Support for parethetical grouping.

Version history:

- 0.5.0: initial release.