arithmexp is a powerful mathematical expression parser and evaluator library for PHP with support for variable substitution, constant declaration, deterministic and non-deterministic function registration, and more.

composer require muqsit/arithmexp

To evaluate a mathematical expression, create a Parser and invoke Parser::parse() with an expression string to obtain a reusable Expression object. Expression::evaluate() returns the value of the expression.

$parser = Parser::createDefault();
$expression = $parser->parse("2 + 3");
var_dump($expression->evaluate()); // int(5)

$expression = $parser->parse("mt_rand()");
var_dump($expression->evaluate()); // int(1370501507)
var_dump($expression->evaluate()); // int(1522981420)

Variables may be substituted at evaluation-time by passing an array<string, int|float|bool> value to Expression::evaluate().

$expression = $parser->parse("x + y");
var_dump($expression->evaluate(["x" => 2, "y" => 3])); // int(5)
var_dump($expression->evaluate(["x" => 1.5, "y" => 1.5])); // float(3)

$expression = $parser->parse("a > b or c");
var_dump($expression->evaluate(["a" => 1, "b" => 2, "c" => true])); // bool(true)

The return value type of the evaluation is consistent with that of PHP's—int + int returns an int value, while float + int|float returns a float value. bool + bool returns an int value, while int || int returns a bool value.