getNationalPrefixFormattingRule() public method

 public function formatNsnUsingPattern($nationalNumber, NumberFormat $formattingPattern, $numberFormat, $carrierCode = null)
 {
     $numberFormatRule = $formattingPattern->getFormat();
     $m = new Matcher($formattingPattern->getPattern(), $nationalNumber);
     if ($numberFormat == PhoneNumberFormat::NATIONAL && $carrierCode !== null && mb_strlen($carrierCode) > 0 && mb_strlen($formattingPattern->getDomesticCarrierCodeFormattingRule()) > 0) {
         // Replace the $CC in the formatting rule with the desired carrier code.
         $carrierCodeFormattingRule = $formattingPattern->getDomesticCarrierCodeFormattingRule();
         $ccPatternMatcher = new Matcher(self::CC_PATTERN, $carrierCodeFormattingRule);
         $carrierCodeFormattingRule = $ccPatternMatcher->replaceFirst($carrierCode);
         // Now replace the $FG in the formatting rule with the first group and the carrier code
         // combined in the appropriate way.
         $firstGroupMatcher = new Matcher(self::FIRST_GROUP_PATTERN, $numberFormatRule);
         $numberFormatRule = $firstGroupMatcher->replaceFirst($carrierCodeFormattingRule);
         $formattedNationalNumber = $m->replaceAll($numberFormatRule);
     } else {
         // Use the national prefix formatting rule instead.
         $nationalPrefixFormattingRule = $formattingPattern->getNationalPrefixFormattingRule();
         if ($numberFormat == PhoneNumberFormat::NATIONAL && $nationalPrefixFormattingRule !== null && mb_strlen($nationalPrefixFormattingRule) > 0) {
             $firstGroupMatcher = new Matcher(self::FIRST_GROUP_PATTERN, $numberFormatRule);
             $formattedNationalNumber = $m->replaceAll($firstGroupMatcher->replaceFirst($nationalPrefixFormattingRule));
         } else {
             $formattedNationalNumber = $m->replaceAll($numberFormatRule);
         }
     }
     if ($numberFormat == PhoneNumberFormat::RFC3966) {
         // Strip any leading punctuation.
         $matcher = new Matcher(self::$SEPARATOR_PATTERN, $formattedNationalNumber);
         if ($matcher->lookingAt()) {
             $formattedNationalNumber = $matcher->replaceFirst("");
         }
         // Replace the rest with a dash between each number group.
         $formattedNationalNumber = $matcher->reset($formattedNationalNumber)->replaceAll("-");
     }
     return $formattedNationalNumber;
 }