This function will format international (10+ digit), non-international (10 digit) or old school (7 digit) phone numbers. Any numbers other than 10+, 10 or 7 digits will remain unformatted.

function formatPhoneNumber($phoneNumber) { $phoneNumber = preg_replace('/[^0-9]/','',$phoneNumber);

if(strlen($phoneNumber) > 10) {
    $countryCode = substr($phoneNumber, 0, strlen($phoneNumber)-10);
    $areaCode = substr($phoneNumber, -10, 3);
    $nextThree = substr($phoneNumber, -7, 3);
    $lastFour = substr($phoneNumber, -4, 4);

    $phoneNumber = '+'.$countryCode.' ('.$areaCode.') '.$nextThree.'-'.$lastFour;
}
else if(strlen($phoneNumber) == 10) {
    $areaCode = substr($phoneNumber, 0, 3);
    $nextThree = substr($phoneNumber, 3, 3);
    $lastFour = substr($phoneNumber, 6, 4);

    $phoneNumber = '('.$areaCode.') '.$nextThree.'-'.$lastFour;
}
else if(strlen($phoneNumber) == 7) {
    $nextThree = substr($phoneNumber, 0, 3);
    $lastFour = substr($phoneNumber, 3, 4);

    $phoneNumber = $nextThree.'-'.$lastFour;
}

return $phoneNumber;

}