README

A voting engine: ballots checked against the rules of their poll, and counted into standings.

phil/poll is the core every vote of an application goes through: a question with one answer, a choice of several options, a ranking of preferences. The rules of a poll say what a ballot may hold — one option, between a minimum and a maximum of options, or options ranked — and whether a blank ballot is an abstention; a ballot is checked against them as a form or a request gives it. A counting method turns the ballots into standings: the count of choices for single and multiple ballots, the instant runoff, the Borda count and the Schulze method for ranked ones. Options tied share their place, an instant runoff keeps its rounds, and abstentions are counted apart.

It is for any PHP application where people vote: a club choosing the date of its next meeting, a community ranking the ideas of its members, an association electing its board, a site asking its readers a question. Who may vote, whether ballots are anonymous and where they are kept belong to the application, or to phil/poll-bundle in Symfony.

It is a plain PHP library with no requirement but PHP. A count reads the ballots once, from any iterable, so a store streams them from its table; the ranked methods group identical rankings, so their memory grows with the distinct rankings rather than with the ballots. The methods keep no state between two counts and are safe to share across the requests of a long-running worker.

Status

Part	State
The rules of a poll: single, multiple and ranked ballots, bounds, abstention, 2 to 100 options	Implemented and tested
Ballots checked against the rules from the values of a form or a request	Implemented and tested
The count of choices: plurality and approval	Implemented and tested
The instant runoff, its rounds, its exhausted ballots and its tie-breaks	Implemented and tested
The Borda count and the Schulze method	Implemented and tested
`CountingMethods`, the methods of an application by name, and the port of a method of its own	Implemented and tested
Polls, ballots and their anonymity in Symfony and Doctrine	Implemented in `phil/poll-bundle`
The single transferable vote of an election with several seats, score and majority judgment ballots	Not started

Documentation

Document	What it covers
Installation	Requirements, installing, a first count.
Rules and ballots	The kinds of ballot, the options, the bounds, the abstention, the checks.
Counting	The four methods, their scores, places, rounds and tie-breaks, and their cost.
Extension points	A counting method of the application.
Exceptions	`PollException` and its three exceptions.
Testing	The library's tests, mutation bar and benchmark, and how to test a count.
Reference	Every type of the library, with its role.

Quick start

composer require phil/poll

use Phil\Poll\CountingMethods;
use Phil\Poll\PollRules;

$rules = PollRules::ranked(['tea', 'coffee', 'cocoa'], abstention: true);

$ballots = [
    $rules->ballot(['coffee', 'tea']),
    $rules->ballot(['tea']),
    $rules->ballot(['tea', 'coffee']),
    $rules->ballot(['cocoa', 'tea']),
    $rules->ballot([]),               // an abstention
];

$result = CountingMethods::defaults()->count('instant_runoff', $rules, $ballots);

$result->winners();                   // ['tea']
$result->standings[0]->place;         // 1
\count($result->rounds);              // 2

Requirements

PHP 8.5 or later.

Contributing

Contributions are welcome on the PHIL monorepo: read the contribution guide and the code of conduct. Report a vulnerability privately, as the security policy explains, never in a public issue.

phil / poll

Package info

Security

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