Social security number formater - PHP Snippet

This php function takes a string of numbers and formats it into a Social Security number format.

Example: formatSSN('123456789'); //returns "123-45-6789"

// Format a Social Security Number. 
function formatSSN($ssn) 
{ 
    return preg_replace("/^(\d{3})(\d{2})(\d{4})$/", "$1-$2-$3", $ssn); 
}