How to replace roman numerals in a string with integers using php?

You can create a PHP function to replace Roman numerals with integers in a string. Here’s a simple example using regular expressions to perform the replacement:

Here’s how to replace Roman numerals in a string with integers using PHP:

Using a loop.

function roman_to_integer($romanString) {
$romanMap = [
'I' => 1,
'V' => 5,
'X' => 10,
'L' => 50,
'C' => 100,
'D' => 500,
'M' => 1000,
$integerValue = 0;
$i = 0;
while ($i < strlen($romanString)) {
$currentChar = $romanString[$i];
if (isset($romanMap[$currentChar])) {
$intValue += $romanMap[$currentChar];
} else {
// Handle invalid Roman numeral (optional)
return "Invalid Roman numeral";
// Alternatively, you can throw an exception or handle it differently
return $integerValue;
$string = "MMXXI";
$integer = roman_to_integer($string);
if ($integer !== false) {
echo "Integer equivalent of '$string': $integer";
} else {
echo "Invalid Roman numeral";


1. The `roman_to_integer` function takes a string containing Roman numerals as input.
2. It defines a dictionary named `$romanMap` that associates each valid Roman numeral with its corresponding integer value.
3. It initializes `$integerValue` to 0 to store the final integer equivalent.
4. A `while` loop iterates through each character in the string:
– `$currentChar` holds the character at the current index.
– It checks if `$currentChar` exists as a key in the `$romanMap` dictionary.
– If it exists, the corresponding integer value is added to `$integerValue`.
– If it doesn’t exist, you can handle the invalid Roman numeral case (e.g., return an error message or throw an exception).
5. The loop continues until the entire string is processed.
6. Finally, the function returns the calculated `$integerValue`.
7. The script demonstrates usage by setting a string variable `$string` containing Roman numerals and calling the function.
8. It checks the return value (`false` for invalid input) and displays the integer equivalent or an error message accordingly.