Pleasehelp me understand this code

[2levelsabove]

What is $dif ???????????

 

 

And why is "$query = "select * from zips where zips.lat < $lat1 AND zips.lat > $lat2 AND zips.lon < $lon1 AND zips.lon > $lon2";"

 

 

used ?

 

 

Please explain.

 

Thank you!!

 

 

@$zipsearch = $_GET['zipsearch'];
@$radius = $_GET['radius'];
$dif = '2';
$results='';
$data=array();

//if(!empty($zipsearch)){}

$query = "select * from zips where zip = '$zipsearch' LIMIT 1";
$result = mysql_query($query);
$row = mysql_fetch_assoc($result);

if(empty($row)){$results = "<tr><td align='center' class='results' style='font-size:16px;font-weight:bold;color:red;font-family:arial;'>Invalid zip code</td></tr>";}

$lat = $row['lat'];$lon = $row['lon'];

$lat1 = ($lat + $dif);
$lat2 = ($lat - $dif);
$lon1 = ($lon + $dif);
$lon2 = ($lon - $dif);

$query = "select * from zips where zips.lat < $lat1 AND zips.lat > $lat2 AND zips.lon < $lon1 AND zips.lon > $lon2";
$result = mysql_query($query);
while($row = mysql_fetch_assoc($result)){
        $dist = great_circle_distance($lat,$row['lat'],$lon,$row['lon']);
        if ($dist < $radius){
        array_unshift($row,$dist);
               $row[0]=round($row[0],2);
               $data[] = $row;
        }
}

sort($data); // $data now has the zip codes and distances in increasing order of distance from $_GET['zipsearch'];

function great_circle_distance($lat1,$lat2,$lon1,$lon2){
               /* Convert all the degrees to radians */
               $lat1 = deg_to_rad($lat1);
               $lon1 = deg_to_rad($lon1);
               $lat2 = deg_to_rad($lat2);
               $lon2 = deg_to_rad($lon2);

               /* Find the deltas */
               $delta_lat = $lat2 - $lat1;
               $delta_lon = $lon2 - $lon1;
       
               /* Find the Great Circle distance */
               $temp = pow(sin($delta_lat/2.0),2) + cos($lat1) * cos($lat2) * pow(sin($delta_lon/2.0),2);

               $EARTH_RADIUS = 3956;

               $distance = $EARTH_RADIUS * 2 * atan2(sqrt($temp),sqrt(1-$temp));

               return $distance;
}

function deg_to_rad($deg){
               $radians = 0.0;
       
               $radians = $deg * M_PI/180.0;

               return($radians);
}

[stuart7398]

http://www.tizag.com/phpT/variable.php

[benphp]

What does the ampersand do?

 

@$zipsearch = $_GET['zipsearch'];

 

 

[unidox]

If there is an error with it, it ignores the error

[haku]

Its actually not very good programming. Programmers put it in to suppress errors, but if the code was written properly in the first place, the errors wouldn't need to be suppressed. Error handling should be handled by writing code to handle it, not by suppressing it.