CODEWITHSUNDEEP
phpmysqlhtmlmath
Dzoki
Dzoki

Reputation: 739

SQL or PHP mistake? Distance calculation

I have a problem with my file. I'm making Travian Clone script and we went really far. Now we decided to add artefacts into game.

Goal is to show closest artefacts to the current village we are in. The code is:

function getDistance($coorx1, $coory1, $coorx2, $coory2) {
          $max = 2 * WORLD_MAX + 1;
          $x1 = intval($coorx1);
          $y1 = intval($coory1);
          $x2 = intval($coorx2);
          $y2 = intval($coory2);
          $distanceX = min(abs($x2 - $x1), $max - abs($x2 - $x1));
          $distanceY = min(abs($y2 - $y1), $max - abs($y2 - $y1));
          $dist = sqrt(pow($distanceX, 2) + pow($distanceY, 2));

          return round($dist, 1);
      }


        unset($reqlvl);
        unset($effect);
        $arts = mysql_query("SELECT * FROM ".TB_PREFIX."artefacts WHERE id > 0");
        $rows = array();
        while($row = mysql_fetch_array($arts)) {
            $query = mysql_query('SELECT * FROM `' . TB_PREFIX . 'wdata` WHERE `id` = ' . $row['vref']);
            $coor2 = mysql_fetch_assoc($query);

            $wref = $village->wid;
            $coor = $database->getCoor($wref);
            $dist = getDistance($coor['x'], $coor['y'], $coor2['x'], $coor2['y']);

            $rows[$dist] = $row;

        }
        ksort($rows, SORT_ASC);
        foreach($rows as $row) {
            echo '<tr>';
            echo '<td class="icon"><img class="artefact_icon_'.$row['type'].'" src="img/x.gif" alt="" title=""></td>';
            echo '<td class="nam">';
            echo '<a href="build.php?id='.$id.'">'.$row['name'].'</a> <span class="bon">'.$row['effect'].'</span>';
            echo '<div class="info">';
            if($row['size'] == 1){
                   $reqlvl = 10;
                   $effect = "village";
               }elseif($row['size'] == 2 OR $row['size'] == 3){
                   $reqlvl = 20;
                   $effect = "account";
               }
            echo '<div class="info">Treasury <b>'.$reqlvl.'</b>, Effect <b>'.$effect.'</b>';
            echo '</div></td><td class="pla"><a href="karte.php?d='.$row['vref'].'&c='.$generator->getMapCheck($row['vref']).'">'.$database->getUserField($row['owner'],"username",0).'</a></td>';
            echo '<td class="dist">'.getDistance($coor['x'], $coor['y'], $coor2['x'], $coor2['y']).'</td>';
            echo '</tr>';
        }
?>

but the code seems to be wrong because its showing all same distances. 14.8 to me. I know i maybe have bad explanation but u will probably understand what I need.

Upvotes: 3

Views: 236

Answers (1)

Clive
Clive

Reputation: 36965

I can't help with your current code I'm afraid but you could try using the Haversine Formula instead:

// Where: 
// $l1 ==> latitude1 
// $o1 ==> longitude1 
// $l2 ==> latitude2 
// $o2 ==> longitude2 
function haversine ($l1, $o1, $l2, $o2) { 
  $l1 = deg2rad ($l1); 
  $sinl1 = sin ($l1); 
  $l2 = deg2rad ($l2); 
  $o1 = deg2rad ($o1); 
  $o2 = deg2rad ($o2); 

  $distance = (7926 - 26 * $sinl1) * asin (min (1, 0.707106781186548 * sqrt ((1 - (sin ($l2) * $sinl1) - cos ($l1) * cos ($l2) * cos ($o2 - $o1))))); 

  return round($distance, 2);
}

Credit goes to this post on go4expert.com, I've used this function in the past and found it works very well.

Upvotes: 3

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