Formula Parser

Formula Parser is a library for parsing and evaluating mathematical formulas given as strings.

Supports:

• Operators: +, -, *, /, ^
• Variables: x, y, z, a, b
• Numbers with decimal point ‘.’
• Numbers in E notation
• Constants: pi, e, Inf
• Functions: sqrt, abs, sin, cos, tan, log, exp
• Unlimited nested parentheses
• NaN (Not a Number)

Installation

Requires PHP 5.4 or higher.

To install with Composer:

composer require denissimon/formula-parser

Usage

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

use FormulaParser\FormulaParser;

$formula = '3*x^2 - 4*y + 3/y';
$precision = 2; // Number of digits after the decimal point

try {
    $parser = new FormulaParser($formula, $precision);
    $parser->setVariables(['x' => -4, 'y' => 8]);
    $result = $parser->getResult(); // [0 => 'done', 1 => 16.38]
} catch (\Exception $e) {
    echo $e->getMessage(), "\n";
}

The $precision parameter has a default of 4, and it’s not required to specify:

$parser = new FormulaParser('3+4*2/(1-5)^8');
$result = $parser->getResult(); // [0 => 'done', 1 => 3.0001]

The initialized object $parser has the following methods:

setValidVariables($array) Overwrites default valid variables.

setVariables($array) Sets variables.

getResult() Returns an array [0 => v1, 1 => v2], where v1 is ‘done’ or ‘error’, and v2 is a computed result or validation error message, respectively.

getFormula() Returns the text of the formula passed to the constructor.

More usage examples can be found in tests/FormulaParserTest.php

License

Licensed under the MIT license