How to determine if a string is a Mathematical statement in PHP?

Question

I have this string for an instance:

"2 + 2 - 2" and when evaluated it should return int(2) ;

I'm looking for a function/parser witch can determine if anykind of math content is matched within a string. More examples:

"(2 + 2) / 2"
"(4 / 8) * 12"
"128 * 8"

Do not need to evaluate and calculate these Math expressions, just need a function witch will determine ( True/False return values), if the statement is of this Math kind.

Is this possible with regex or something? Thanks!

Answer 1

Maybe run it as php on runtime and check that the responding value comes back as numeric. Take a look at this. http://php.net/manual/en/function.eval.php

Answer 2

See eval . For example, you can do this:

$result = INF;
try { 
  eval("$result=" + myMathExpression);  // Evaluate here
} catch (Exception $e) { 

} 
if($result != INF) echo("Expression is a valid mathematical expression.");

Just be careful, because any PHP code will be evaluated!

Answer 3

If you know what type of expressions you will be parsing you could try to use regular expressions. Something like ^\\d+\\s*(\\+|-|\\*|\\\\)\\s*\\d+ should yield true if you are trying to validate the binary operators of + , * , - and \\ . So it would validate items such as 3 + 3 , 2 - 0 , etc.

Answer 4

You can use a parser generator from XP-framework. See sample grammar for calculator, which can be translated to PHP code.