/**
 * 阿拉伯数字和罗马数字相互转换
 *
 * @param 计算给定数字的罗马字符串的函数
 * @arrange (512.笔记) jb51.cc
 **/
function dec2roman($f) 
{ 
	// Return false if either $f is not a real number,$f is bigger than 3999 or $f is lower or equal to 0:         
		if(!is_numeric($f) || $f > 3999 || $f <= 0) return false;
	// Define the roman figures: 
		$roman = array('M' => 1000,'D' => 500,'C' => 100,'L' => 50,'X' => 10,'V' => 5,'I' => 1); 
 
	// Calculate the needed roman figures: 
		foreach($roman as $k => $v) if(($amount[$k] = floor($f / $v)) > 0) $f -= $amount[$k] * $v; 
	 
	// Build the string: 
		$return = ''; 
		foreach($amount as $k => $v) 
		{ 
			$return .= $v <= 3 ? str_repeat($k,$v) : $k . $old_k; 
			$old_k = $k;                 
		} 
	 
	// Replace some spacial cases and return the string: 
		return str_replace(array('VIV','LXL','DCD'),array('IX','XC','CM'),$return); 
} 

// echo dec2romen(1981); 


// Function to get the decimal value of a roman string: 
function roman2dec($str = '') 
{ 
	// Return false if not at least one letter is in the string: 
		if(is_numeric($str)) return false; 
 
	// Define the roman figures: 
		$roman = array('M' => 1000,'I' => 1); 
 
	// Convert the string to an array of roman values: 
		for($i = 0; $i < strlen($str); $i++) if(isset($roman[strtoupper($str[$i])])) $values[] = $roman[strtoupper($str[$i])]; 
	 
	// Calculate the sum of that array: 
		$sum = 0; 
		while($current = current($values)) 
		{ 
			$next = next($values); 
			$next > $current ? $sum += $next - $current + 0 * next($values) : $sum += $current; 
		} 
	// Return the value: 
		return $sum; 
} 
// echo roman2dec(IX);         


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