<?php
/* formats a 10 or 7 digit phone number (number only) by adding dashes at the appropriate locations */

function phoneFormat($number) {
if(ctype_digit($number) && strlen($number) == 10) {
  $number = substr($number, 0, 3) .'-'. substr($number, 3, 3) .'-'. substr($number, 6);
} else {
if(ctype_digit($number) && strlen($number) == 7) {
$number = substr($number, 0, 3) .'-'. substr($number, 3, 4);
}
}
return $number;
}

echo  phoneFormat(8297243489);

?>

829-724-3489