Automattic\Phone\Mobile_Validator::normalize PHP Method

    function normalize($phone_number, $country_name = null)
    {
        if (empty($phone_number) || !is_string($phone_number)) {
            return array();
        }
        if (empty($country_name) || !is_string($country_name)) {
            $country_name = "";
        }
        $phone_number = trim($phone_number);
        $country_name = trim($country_name);
        $is_plus_prefixed = preg_match("/^\\+/", $phone_number);
        // comment originated from node-phone:
        // remove any non-digit character, included the +
        $phone_number = preg_replace("/\\D/", "", $phone_number);
        $iso3166_entry = $this->get_iso3166_entry($country_name);
        if (empty($iso3166_entry)) {
            return array();
        }
        if ($country_name) {
            $alpha3 = $iso3166_entry["alpha3"];
            // comment originated from node-phone:
            // remove leading 0s for all countries except 'GAB', 'CIV', 'COG'
            if (!in_array($alpha3, array("GAB", "CIV", "COG"))) {
                $phone_number = preg_replace("/^0+/", "", $phone_number);
            }
            // comment originated from node-phone:
            // if input 89234567890, RUS, remove the 8
            if ("RUS" == $alpha3 && 11 == strlen($phone_number) && preg_match("/^89/", $phone_number)) {
                $phone_number = preg_replace("/^8+/", "", $phone_number);
            }
            if ($is_plus_prefixed) {
                // comment originated from node-phone:
                // D is here.
            } else {
                // comment originated from node-phone:
                // C: have country, no plus sign --->
                //	case 1
                //		check phone_number_length == phone.length
                //		add back the country code
                //	case 2
                //		phone_number_length+phone_country_code.length == phone.length
                //		then go to D
                if (in_array(strlen($phone_number), $iso3166_entry["phone_number_lengths"])) {
                    $phone_number = $iso3166_entry["country_code"] . $phone_number;
                }
            }
        } else {
            if ($is_plus_prefixed) {
                // comment originated from node-phone:
                // A: no country, have plus sign --> lookup country_code, length, and get the iso3166 directly
                // also validation is done here. so, the iso3166 is the matched result.
                $iso3166_entry = $this->get_iso3166_by_phone($phone_number);
            } else {
                // comment originated from node-phone:
                // B: no country, no plus sign --> treat it as USA
                // 1. check length if == 11, or 10, if 10, add +1, then go go D
                // no plus sign, no country is given. then it must be USA
                if (in_array(strlen($phone_number), $iso3166_entry["phone_number_lengths"])) {
                    $phone_number = "1" . $phone_number;
                }
            }
        }
        if ($this->validate_phone_iso3166($phone_number, $iso3166_entry)) {
            return array("+" . $phone_number, $iso3166_entry["alpha3"]);
        } else {
            return array();
        }
    }