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Role: Documentation
Content type: text/markdown
Description: Description of class functionality and use cases
Class: Equation Operating System
Solve equations with multiple variables
Author: By
Last change: Added development note

On README for developing classes to add new functions.
Link update

PHPUnit should be simpler to run now
Merge branch 'master' of
Merge pull request #9 from elliotwms/master

Commenting consistency
Date: 7 months ago
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Install EOS with Composer

Add the dependency:

"require": {
    "jlawrence/eos": "3.*"

Run composer update and you're done.

Equation Operating System


This class makes it incredibly easy to use and parse/solve equations in your own applications. __NOTE__ ALL of the functions within these classes are static. It is also important to note that these classes throw exceptions if running in to errors, please read the beginning of the Math.php file for the defines of the exceptions thrown. Exceptions includes a descriptive message of the error encountered and within Parser will also typically include the full equation used.


This class has one important function, Parser::solve() which does all the legwork, so we'll start there and end with examples.

use jlawrence\eos\Parser;

solve($infix, $variables)

To use this function:

$value = Parser::solve($eq, $vars);


Is simply a standard equation with variable support.

Example Equations:


The parser has good implied multiplication.


The variables are fairly simple to understand. If it contains a scalar (ie a non-array value) _every_ variable within the equation will be replaced with that number. If it contains an array, there will be a by-variable replacement - note that the array MUST be in the format of 'variable' => value Such as:

    'x' => 2,
    'y' => 3

Given the equation:


If this is called by:

Parser::solveIF('5x^y', 2);

It will equal '20', as every variable is replaced by 2. However, if called like:

Parser::solveIF('5x^y', array(
                            'x' => 2,
                            'y' => 3));

You will get the result of '40' as it would equate to 5*2^3, as expected.


To use:

use jlawrence\eos\Graph;

This is the fun class that can create graphs. The image will default to 640x480, to initialize a different size use:

Graph::init($width, $height);

The $width and $height are the values used for the image size.

graph($eq, $xLow, $xHigh, [$xStep, $xyGrid, $yGuess, ...])

This method will generate the graph for the equation ($eq) with a min and max x range that it will parse through. All Variables explained:

  • $eq The Standard Equation to use. _Must_ have a variable in it. (ie x)
  • $xLow The starting point for the calculations - the left side of the graph.
  • $xHigh The last point calculated for the variable - the right side of the graph.
  • $xStep Stepping point for the variable. Set to null/false to use the smart xStep feature within the graph class.
  • $xyGrid = false Show x/y gridlines on the graph. Defaults to false. Each grid line is set at an integer, with a max of 30 lines, so it will calculate the stepping for it. When the grid is show, the lines are labeled along the top and left side of the image.
  • $yGuess = true Guess the Lower and Upper y-bounds (The bottom and top of the image respectively.) This will set the the bounds to the lowest y value encountered for the $yLow, and the largest y value for $yHigh.
  • $yLow = null Lower bound for y. Will be reset if a lower value for y is found if $yGuess is true.
  • $yHigh = null Upper bound for y. Will be reset if a larger y value is found if $yGuess is true.

If you don't want the axis' labeled with their numbers, you can turn off the default behavior with:

Graph::$labelAxis = false;


  • Allow user-defined colors for all aspects of the graph.

To set up a graph with a 21x21 window (ie -10 to 10) for the equation sin(x) and output as PNG, would use as:

Graph::graph('sin(x)', -10, 10, 0.01, true, false, -10, 10);

It would look like: Sin(x)



Run the unit tests by first installing phpunit with (from the repository root)

composer update

Then run the tests with


When creating classes for adding functions to the package, make sure to call Parser::solveIF() instead of Parser::solve() so that the class retains the full original equation used by the user.