Convert Roman Number To Integer - Interview Problem Solving Question | PHP

In this post we are going to see a very popular question in interview, Convert roman number to integer. we are going to write a program for that case. we are going to create a function which is accept the Roman string and convert to it's appropriate integer.

The string which i have need to pass that function must be valid roman string.

function romanToInt($s) {
        
       //write all roman numerals and it's correspondence integer
        $numerals = array(
                        'I' => 1,
                        'V' => 5,
                        'X' => 10,
                        'L' => 50,
                        'C' => 100,
                        'D' => 500,
                        'M' => 1000,
                        '' => 0,
                        );
        $num = 0;

        $s = str_split($s); //converting string to array

        foreach($s as $key => $roman){

            if($key > 0 && $numerals[$roman] > $numerals[$s[$key - 1]] && $previous_numeral != $roman){
                $num = $num - $numerals[$s[$key - 1]] +  $numerals[$roman] - $numerals[$s[$key - 1]];
                
            }else{
                $num += $numerals[$roman];
            }


        }


return $num;

    }

This is the solution of convert roman to numerals.