PEAR Manual
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Numbers_Roman

Numbers_Roman provides methods to convert Arabic numbers like 23 into Roman numerals like XXIII and back.

Note: Both class methods are static; you do not need to instantiate an object.

Converting Arabic to Roman Numerals

The static method toNumeral does exactly this. It can be used for numbers from 1 to 5 999 999. Using it to convert higher numbers works, but does not produce historically correct results.

The second parameter $uppercase determines if the letters should be UPPERCASE (default) or not. Parameter number 3 sets if HTML code for overscores shall be generated; this is necessary for numbers greater than 3999. If the parameter is set to false, letters will be prefixed with an underscore _.

Example 52-1. Converting Arabic numbers to Roman numerals

<?php
require_once 'Numbers/Roman.php';

echo Numbers_Roman::toNumeral(23);
//returns: XXIII

echo Numbers_Roman::toNumeral(23, false);
//returns: xxiii
?>

Converting Roman Numerals to Arabic numbers

Using the static method toNumber you can convert Roman numerals like XLII to Arabic numbers like 42. Letters prefixed with an underscore represent numbers larger than 1000.

Table 52-1. Conversion Table: Roman letter to Arabic number

Roman	Arabic
I	1
V	5
X	10
L	50
C	100
D	500
M	1000
S, _V	5000
R, _X	10 000
P, _L	50 000
Q, _C	100 000
O, _D	500 000
N, _M	1 000 000

Example 52-2. Converting Roman numerals to Arabic numbers

<?php
require_once 'Numbers/Roman.php';

echo Numbers_Roman::toNumber('XLII');
//returns: 42
?>