Calculate a sum in a string

Question

I have string like this: $string = \"a + b + c\";. Now I would like to calculate the string as sum.

For example:

$a = 10;
$b = 10;
$c =          


        

Answer 1

I once made a calculator script.

• It parses the calculation and puts each number and operator on a stack, in reverse polish notation.
• It calculates the results by executing operations all operations on the stack.