怎么样使用PHP计算年龄？

/**
* $date是时间戳
* $type为1的时候是虚岁,2的时候是周岁
*/
function getAgeByBirth($date,$type = 1){
  $nowYear = date("Y",time());
  $nowMonth = date("m",time());
  $nowDay = date("d",time());
  $birthYear = date("Y",$date);
  $birthMonth = date("m",$date);
  $birthDay = date("d",$date);
  if($type == 1){
  $age = $nowYear - ($birthYear - 1);
  }else{$type == 2}{
  if($nowMonth<$birthMonth){
   $age = $nowYear - $birthYear - 1;
  }elseif($nowMonth==$birthMonth){
   if($nowDay<$birthDay){
   $age = $nowYear - $birthYear - 1;
   }else{
   $age = $nowYear - $birthYear;
   }
  }else{
   $age = $nowYear - $birthYear;
  }
  }
  return $age;
}