PHP - usort正在修改数组中对象的内容,我该如何防止这种情况?

I am using usort with a user comparison function to sort an array of objects. After running usort on an array of these objects, I've found that some of the values of the objects have changed along with their position in the array. What am I missing? I don't believe there are any side effects in my user comparison function. Does usort deconstruct/reconstruct objects some how?

Here is the the user comparison function I'm using:

private function SortArrayOfSegments($segments){
    foreach($segments as $segment){
        echo '<pre>';
        var_dump($segment);  
    }
    usort($segments, "AirObject::CompareSegments");
    foreach($segments as $segment){
        var_dump($segment);
        echo '</pre>';
     }
    return $segments;
}

public static function CompareSegments($a, $b){
    $interval = date_diff(date_create($a->StartDateTime->GetString()),
                date_create($b->StartDateTime->GetString()));
    if($interval->invert == 1){
        return 1;   
    }else if($interval->y == 0 && $interval->m == 0  && $interval->d == 0 
    && $interval->i == 0 && $interval->s == 0 && $interval->h == 0){
        return 0;   
    }else if($interval->invert == 0){
        return -1;  
    }  
}

The objects I'm using look like this :

object(AirSegment)#14 (12) {
      ["StartDateTime"]=>
      object(VDateTime)#27 (4) {
        ["date"]=>
        string(10) "2010-12-07"
        ["time"]=>
        string(8) "09:23:21"
        ["timezone"]=>
        string(0) ""
        ["utc_offset"]=>
        string(0) ""
      }
      ["EndDateTime"]=>
      object(VDateTime)#23 (4) {
        ["date"]=>
        string(10) "2010-12-07"
        ["time"]=>
        string(8) "13:23:21"
        ["timezone"]=>
        string(0) ""
        ["utc_offset"]=>
        string(0) ""
      }
      ["start_airport_code"]=>
      string(3) "SFO"
      ["start_city_name"]=>
      string(13) "San Francisco"
      ["end_airport_code"]=>
      string(3) "STL"
      ["end_city_name"]=>
      string(8) "St Louis"
      ["operating_airline"]=>
      string(15) "United Airlines"
      ["operating_flight_number"]=>
      string(3) "335"
      ["duration"]=>
      float(NAN)
      ["required_properties":protected]=>
      array(9) {
        ["StartDateTime"]=>
        bool(false)
        ["EndDateTime"]=>
        bool(false)
        ["start_airport_code"]=>
        bool(false)
        ["end_airport_code"]=>
        bool(false)
        ["operating_airline"]=>
        bool(false)
        ["operating_flight_number"]=>
        bool(false)
        ["start_city_name"]=>
        bool(false)
        ["end_city_name"]=>
        bool(false)
        ["service_class"]=>
        bool(true)
      }
      ["service_class"]=>
      string(5) "Coach"
      ["trip_id"]=>
      string(4) "1621"
    }

The property that is changing is the duration property. Before usort is run, every object has a valid float value. After usort, two of them are NaN.

RESOLUTION:

date_diff has side effects -- at least in my build of PHP. Removing it fixed the issues entirely.

public static function CompareSegments($a, $b){
    $adate = new DateTime($a->StartDateTime->GetString());
    $bdate = new DateTime($b->StartDateTime->GetString());
    $lessThan = $adate < $bdate;
    $equal = $adate == $bdate;
    $greaterThan = $adate > $bdate;

    if($lessThan){
        return -1;  
    }else if($equal){
        return 0;   
    }else{
        return 1;   
    }
}
查看全部
dqyuipw44576
dqyuipw44576
2010/12/12 01:02
  • sorting
  • php
  • 点赞
  • 收藏
  • 回答
    私信
满意答案
查看全部

2个回复