PHP dynamic maths operator issue

Question

I have the below code snippet which will cast an input to a float and create a variable maths operator of either > or < based on whether the float is a positive or negative number.

// allow custom variance from user input
if (isset($request->custom_variance)) {
    $variance_amount = floatval($request->custom_variance);
    ($variance_amount < 0) ? $operator = " < " : $operator = " > ";
} else {
    // set default
    $variance_amount = floatval(-50);
    $operator = " < ";
}

I then use these variables in an if statement, I have dumped here to show the output:

 var_dump((floatval($value_one) - floatval($value_two)).$operator.$variance_amount);
// returns "-51.35 < -50"

If I hard code the values I get this (It works as I want a Boolean)

 var_dump((floatval($value_one) - floatval($value_two)) < -50);
// returns true

I have done some reading on here about this and it seems like it isn't working as my operator is being interpreted as a string but I would like to avoid using the eval() function if possible.

Any suggestions?

A l w a y s S u n n y · Accepted Answer · 2017-06-26 13:47:15Z

1

You can try with the eval() with proper string expression like this with return keyword and ; and then use if condition as you wish.

$result="return ((floatval($value_one)- floatval($value_two)).$operator.$variance_amount);";
  // returns true instead of "-51.35 < -50"
  if(eval($result)){
    // do what ever you want to do
   }

edited Jun 26, 2017 at 13:47

answered Jun 26, 2017 at 11:07

A l w a y s S u n n y

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