If you want to display a number ending with ,- (like 200,-) when there are no decimal characters and display the decimals when there are decimal characters i use:
function DisplayDouble($value)
 {
 list($whole, $decimals) = split ('[.,]', $value, 2);
 if (intval($decimals) > 0)
 return number_format($value,2,".",",");
 else
 return number_format($value,0,".",",") .",-";
 }