Calculon

Calculon is a mathematical expression parser and evaluator for PHP, built on a proper AST (Abstract Syntax Tree) architecture. Named after the melodramatic acting robot from Futurama, it combines serious functionality with entertaining error messages.

Use it whenever you need to evaluate user-provided mathematical formulas safely — pricing rules, discount calculations, shipping cost formulas, or any scenario where business users need to define their own calculations without touching PHP code.

GitHub: qoliber/calculon

Installation

composer require qoliber/calculon

Requires: PHP 8.1+

Key Features

• Safe evaluation — User-provided expressions are parsed into an AST and evaluated without eval(). No code injection possible.
• Variables — Pass runtime values into expressions: price * quantity * (1 - discount)
• Built-in functions — sin, cos, sqrt, log, abs, ceil, floor, round, min, max, pow
• Constants — PI and E pre-defined, register your own
• Percentage calculations — Context-aware: 100 + 10% = 110, not 100.1
• Custom functions — Implement FunctionInterface to add domain-specific functions (tax calculation, currency conversion, margin formulas)
• Validation — Validate expressions without evaluating them, useful for form validation
• Variable extraction — Automatically discover which variables a formula requires

Architecture

Clean four-stage pipeline:

1. Lexer — Tokenizes the input string into meaningful tokens
2. Parser — Builds an Abstract Syntax Tree respecting operator precedence
3. AST Nodes — Typed representation of the expression structure
4. Evaluator — Traverses the tree using the Visitor pattern, resolving values

Performance

Benchmarked on real-world expressions:

Quality

• 192 unit tests, 495 assertions
• 100% code coverage
• 97% mutation score (Infection)
• PHPStan level 8

License

MIT License