README

PHP classes for working with, and solving, quadratic equations.

What Is A Quadratic Equation?

A quadratic equation is a univariate polynomial with degree of 2, that is then set to equal zero so that the indeterminate can be determined:

ax² + bx + c = 0

Equations can often be solved with factoring or completing the square, but there is also a Quadratic Formula:

The QuadraticEquation interface constructor accepts values for a, b and c and the Solver can return one or both roots, including imaginary roots.

Installation

composer require gamajo/quadratic

Requires PHP 7.

Usage

Basic Usage

Create an equation object, pass that to the solver, solve, and retrieve the roots:

use Gamajo\Quadratic;

// Represents x^2 + 5x + 6 = 0.
$equation = new BasicQuadraticEquation(1, 5, 6);

$solver = new Solver($equation);
$solver->solve();

echo $solver->get(); // '2 and 3'
echo $solver->get('root1'); // '2'
echo $solver->get('root2'); // '3'

The Solver has no problem with complex roots:

use Gamajo\Quadratic;

// Represents 3x^2 + 4x + 5 = 0.
$equation = new BasicQuadraticEquation(3, 4, 5);

$solver = new Solver($equation);
$solver->solve();

echo $solver->get(); // '-0.667 + 1.106i and -0.667 - 1.106i'

BasicQuadraticEquation Methods

The BasicQuadraticEquation class implements the QuadraticEquation interface, which in turn extends the Equation interface. As such, it supports the following methods:

use Gamajo\Quadratic;

// Represents x^2 + 5x + 6 = 0.
$equation = new BasicQuadraticEquation(1, 5, 6);

echo $equation->getA(); // 1
echo $equation->getB(); // 5
echo $equation->getC(); // 6
print_r( $equation->getArgsAsArray() ); // [1, 5, 6]

There is also a hasValidArguments() method, but as this library uses scalar type declarations, the manual check to see if they are all integers is somewhat redundant.

Solver Methods

The Solver class can optionally set the maximum decimal place precision of the roots:

use Gamajo\Quadratic;

// Represents 8x^2 + 5x - 2 = 0.
$equation = new BasicQuadraticEquation(8, 5, -2);

$solver = new Solver($equation);
$solve->setPrecision(4); // Default precision is 3

echo $solve->getPrecision(); // 4

$solver->solve();

echo $solver->get(); // '-0.9021 and 0.2771' instead of '-0.902 and 0.277'

Change Log

See the change log.

License

MIT.

Contributions

Contributions are welcome - fork, fix and send pull requests against the develop branch please.

Credits

Built by Gary Jones.
Original procedural code version, copyright 2004 Gary Jones.
This version copyright 2016 Gamajo Tech