Formula1

Simple Mathematical formulas evaluator for PHP

If you need to evaluate a formula with basic operators and variables, and

• No eval: You dont want to use EVAL for obvious security reasons,
• No dependencies: You don't want to rely on half the internet as dependencies, but prefer a single self-contained class,
• Old PHP OK: You don't necessarily have the latest PHP version, or Composer,
• No spaghetti: You want something readable that you could easily understand and customize,
• Arithmetic rules OK: You need something that knows about operators priority, unary operators, and parenthesis,
• Rounding OK: You want to specify a precision and rounding mode for the result,
• Recursive eval: You want to be able to include sub-formulas inside your variables,
• Arrays OK: You need to use indexed or key-value arrays as variable inside the formula,
• functions OK: You need to use basic math functions inside the formula,
• Errors OK: You need to have a human-friendly message telling why the formula is wrong when it is,

...then you gonna like Formula1 ! ;-)

Simple usage no variables

$f1 = new Formula1('-45+(41*2)-(6/(3+1))');
echo($f1->compute()); // 35.5

// With rounding (third and fourth params are precision and mode, like for the round function) 
$f1 = new Formula1('2/3', [], 3);
echo($f1->compute()); // 0.667

Simple usage with variables

$f1 = new Formula1('-45+(fourty_one*2)-(6/(three+1))' , ['fourty_one'=>41, 'three'=>3]);
echo($f1->compute()); // 35.5

Funky usage with variables that include formulas themselves (and recusrively)

$f1 = new Formula1('-45+(fourty_one*2)-(6/(three+1))' , ['fourty_one'=>'82/2', 'three'=>'12/four', 'four'=>4]);
echo($f1->compute()); // 35.5

Display parsing error if any

$f1 = new Formula1('-45+(fourty_one*2)-(6/(three+1)))' , ['fourty_one'=>'82/2', 'three'=>'12/four', 'four'=>4]);
if($f1->parse_error=='') echo($f1->compute()); 
else echo($f1->parse_error."<br>\n"); // Too many closing parenthesis !

Using an indexed array

$f1 = new Formula1('toto*primes[6]',['toto'=>10,'primes'=>[2,3,5,7,11,13,17,19,23,29,31]]);
echo($f1->compute()."<br>\n"); //170

Using a key-value array

$f1 = new Formula1('toto*myar["zorglub_99"]',['toto'=>10,'myar'=>['aaa'=>2.5,'zorglub_99'=>5.5]]);
echo($f1->compute()."<br>\n"); //55

Using math functions

$f1 = new Formula1('2*5+sin(pi()/4)');
echo($f1->compute()."<br>\n"); //7.071...

TODO

• Would be better to give parameters in the compute, to allow one parsing => many compute, with different values sets, but this needs a rewrite of the current parse-compute split.
• The index of indexed arrays should be evaluated to allow formulas as indexes, but this needs a rewrite of the current parse-compute split.

Known bugs

• Won't allow unary operator directly following a binary operator like "5*-x" or "5+-x". Your can workaround by using parenthesis like "5*(-x)" or "5+(-x)"