function isValidFormat($s) {
$pattern = "/^(\\d{3}-)?\\d{3}-\\d{4}$/";
return preg_match($pattern, $s) === 1;
}
$s = "771-290-1652";
if (isValidFormat($s)) {
echo "Valid\n";
} else {
echo "Not Valid\n";
}
$s = "771-29-162";
if (isValidFormat($s)) {
echo "Valid\n";
} else {
echo "Not Valid\n";
}
$s = "771-AB1-1620";
if (isValidFormat($s)) {
echo "Valid\n";
} else {
echo "Not Valid\n";
}
/*
run:
Valid
Not Valid
Not Valid
*/