php-invariant

Yet another assertion library.

Installation

You can install this library via composer:

$ composer require zheltikov/php-invariant

Usage

The main function to be used in this library is invariant. This function is intended to indicate a programmer error for a condition that should never occur, similar to assertions. For example:

<?php

require_once(__DIR__ . '/../vendor/autoload.php');

use function Zheltikov\Invariant\invariant;

$obj = new DateTime();
invariant($obj instanceof DateTime, 'Object must have type DateTime');

$p = 123;
invariant($p !== null, 'Value can\'t be null');

$max = 100;
invariant($p !== null && $p <= $max, '$p\'s value %d must be <= %d', $p, $max);

If the first argument value evaluates to true, the program continues execution; otherwise, the function invariant_violation is called. That function either throws an InvariantException, or calls the handler previously registered by the function invariant_callback_register.

The first argument is evaluated as a boolean expression. The second argument is a string that can contain text and/or optional formatting information as understood by the function sprintf. The optional comma-separated list of values following the string must match the set of types expected by the optional formatting information inside that string.

TODO

• Build a functional-style assertion library
• Build an object-oriented interface for these functions