use rizalmf\formula\DeductiveFormula;
use rizalmf\formula\exception\FormulaException;

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

$formula = new DeductiveFormula();

try {
    $expression = '{foo}^({bar}/2+(2+3^(1/2)))';
    $requestedVariables = $this->formula->setFormula($expression);
    var_dump($requestedVariables);

} catch (FormulaException $e) {
    // handle Exceptions
}

// output : array ([0] => "foo", [1] => "bar")

    // ...

    // 1. define value per variable
    $this->formula->setVariable("foo", 4);
    $this->formula->setVariable("bar", 1);

    // 2. use array
    $this->formula->setVariables([
        "foo" => 4,
        "bar" => 1
    ]);

    // ...

    // 1. get value from specific variable
    var_dump($this->formula->getVariable("foo"));
    // output : 4

    // 2. get values all variables
    var_dump($this->formula->getVariables());
    // output : array ([foo] => 4, [bar] => 1)

    // 1. get possible variables from Formula
    var_dump($this->formula->getRequestedVariables());
    // output : array ([0] => "foo", [1] => "bar")

    $result = $this->formula->execute();
    var_dump($result);

    // output : 353.141268350837

    // (optional) set limit iteration calculating machine. default 200
    $formula->setLimit(50);

    // debug
    $result = $this->formula->execute(true);
    var_dump($result);

    // output : 
    // iteration-1 => 4^(1/2+(2+3^(1/2)))
    // iteration-2 => 4^(1/2+(2+3^0.50))
    // iteration-3 => 4^(1/2+(2+1.73205080756888))
    // iteration-4 => 4^(1/2+3.73205080756888)
    // iteration-5 => 4^(0.50+3.73205080756888)
    // iteration-6 => 4^4.23205080756888
    // 353.141268350837

    FormulaException
        |- BadFormulaException