php - 谷歌地图商店定位器

Question

您好，我正在学习 Google 上的创建商店定位器教程，可以在此处找到。

https://developers.google.com/maps/articles/phpsqlsearch_v3#findnearsql

我的代码是

    // Select all the rows in the markers table
$query = sprintf("SELECT address, name, lat, lng, ( 3959 * acos( cos( radians('%s') ) * cos( radians( lat ) ) * cos( radians( lng ) - radians('%s') ) + sin( radians('%s') ) * sin( radians( lat ) ) ) ) AS distance FROM markers HAVING distance < '%s' ORDER BY distance LIMIT 0 , 20",
  mysql_real_escape_string("37.414832"),
  mysql_real_escape_string("-122.024857"),
  mysql_real_escape_string("37.414832"),
  mysql_real_escape_string("10"));


$result = mysql_query($sql);

if (!$result) 
{
  die('Invalid query: ' . mysql_error());
}
else
{
    echo 'success';
}

// Start XML file, echo parent node
echo "<markers>\n";
// Iterate through the rows, printing XML nodes for each
while ($row = @mysql_fetch_assoc($result)){
  $node = $dom->createElement("marker");
  $newnode = $parnode->appendChild($node);
  $newnode->setAttribute("name", $row['name']);
  $newnode->setAttribute("address", $row['address']);
  $newnode->setAttribute("lat", $row['lat']);
  $newnode->setAttribute("lng", $row['lng']);
  $newnode->setAttribute("distance", $row['distance']);
}


// End XML file
echo "</markers>\n";
echo $dom->saveXML();

但是当我运行脚本时，我收到了错误消息

This page contains the following errors:
error on line 1 at column 1: Document is empty
Below is a rendering of the page up to the first error.

有人能看出我的代码有什么问题吗？

Answer 1

$dom您尝试为其创建元素的对象在“while”循环之前不存在。首先创建该 DOMDocument 对象并包含 <markers>该对象中的根节点。