I am using the Google Maps API with parts in javascript and others in PHP.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
  
    
    Google Maps AJAX + mySQL/PHP Example
    
    
    //
var iconBlue = new GIcon(); 
iconBlue.image = 'icon.png';
iconBlue.shadow = '';
iconBlue.iconSize = new GSize(19, 19);
iconBlue.shadowSize = new GSize(22, 20);
iconBlue.iconAnchor = new GPoint(6, 20);
iconBlue.infoWindowAnchor = new GPoint(5, 1);
var iconRed = new GIcon(); 
iconRed.image = 'icon.png';
iconRed.shadow = '';
iconRed.iconSize = new GSize(19, 19);
iconRed.shadowSize = new GSize(22, 20);
iconRed.iconAnchor = new GPoint(6, 20);
iconRed.infoWindowAnchor = new GPoint(5, 1);
var customIcons = [];
customIcons["restaurant"] = iconBlue;
customIcons["bar"] = iconRed;
function load() {
  if (GBrowserIsCompatible()) {
    var map = new GMap2(document.getElementById("map"));
    map.setMapType(G_SATELLITE_MAP);
    map.addControl(new GSmallMapControl());
    map.addControl(new GMapTypeControl());
    map.setCenter(new GLatLng(47.614495, -122.341861), 13);
    // Change this depending on the name of your PHP file
    GDownloadUrl("phpsqlajax_genxml.php", function(data) {
      var xml = GXml.parse(data);
      var markers = xml.documentElement.getElementsByTagName("marker");
      for (var i = 0; i < markers.length; i++) {
        var name = markers[i].getAttribute("name");
        var address = markers[i].getAttribute("address");
        var type = markers[i].getAttribute("type");
        var point = new GLatLng(parseFloat(markers[i].getAttribute("lat")),
                                parseFloat(markers[i].getAttribute("lng")));
        var marker = createMarker(point, name, address, type);
        map.addOverlay(marker);
      }
    });
  }
}
function createMarker(point, name, address, type) {
  var marker = new GMarker(point, customIcons[type]);
  var html = "<b>" + name + "</b> <br/>" + address;
  GEvent.addListener(marker, 'click', function() {
    marker.openInfoWindowHtml(html);
  });
  return marker;
}
//]]>
  
    
  
(I suppose the php will be called by "GDownloadUrl("phpsqlajax_genxml.php", function(data) {
..." in the javascript part of the sourcecode of phpsqlajax_map.htm)
Now I need another php file and the code snipplets for it, which creates an input form where I can add some new locations to the google map. Following code is used to create the xml file here: http://detektors.de/maptest/phpsqlajax_genxml.php
The next step would be, trying to make an plugin for wordpress that I could easily post a blog entry with a new location on the same map, which displays already some other locations stored in the mysql database.
thanks!
<?php
require("phpsqlajax_dbinfo.php");
function parseToXML($htmlStr) 
{ 
$xmlStr=str_replace('<','<',$htmlStr); 
$xmlStr=str_replace('','>',$xmlStr); 
$xmlStr=str_replace('"','"',$xmlStr); 
$xmlStr=str_replace("'",''',$xmlStr); 
$xmlStr=str_replace("&",'&',$xmlStr); 
return $xmlStr; 
} 
// Opens a connection to a MySQL server
$connection=mysql_connect ($host, $username, $password);
if (!$connection) {
  die('Not connected : ' . mysql_error());
}
// Set the active MySQL database
$db_selected = mysql_select_db($database, $connection);
if (!$db_selected) {
  die ('Can\'t use db : ' . mysql_error());
}
// Select all the rows in the markers table
$query = "SELECT * FROM markers WHERE 1";
$result = mysql_query($query);
if (!$result) {
  die('Invalid query: ' . mysql_error());
}
header("Content-type: text/xml");
// Start XML file, echo parent node
echo '';
// Iterate through the rows, printing XML nodes for each
while ($row = @mysql_fetch_assoc($result)){
  // ADD TO XML DOCUMENT NODE
  echo '';
}
// End XML file
echo '';
?