My first PHP, needs criticism

 #Get variables passed to this page
 icon=$_GET['id'];
 map=$_GET['map'];
 path=$_GET['path'];
 x=$_GET['x'];
 y=$_GET['y'];
 
 # to load xml from a file
 $doc = xmldocfile( ".../map.xml" ) or die("Database could not be loaded");
 
 # get root node "guilds"
 $guilds = $doc->root();
 
 #create xpath expression to test for existence of an icon with the id tag:
 $xp = new domxpath($doc)
 $result = $xp->query("/guilds/icon[@id=$icon]")
 
 #If icon of id exists, update information
 if($result!=Null){
    $result.childNodes[0]->data = $map
    $result.childNodes[1]->data = $path
    $result.childNodes[2]->data = $x
    $result.childNodes[3]->data = $y
 }
 #else create nodes with information,
 else {
    //create <icon> node under guilds node
    $iconNode = make_node($guilds,"icon","");
    //set id attribute
    $iconNode->setattr("id",icon);
    //create nodes under <icon>
    $iconNode->new_child("map",$map)
    $iconNode->new_child("path",$path)
    $iconNode->new_child("x",$x)
    $iconNode->new_child("y",$y)
 }
 
 #save doc
 $doc->save(".../map.xml");
 
 //////////////////////////
 # function for making child nodes
 function make_node($parent,$name,$content)
 {
    # adds a new child node to parent node
    $parent->new_child($name,$content);
 
    # return the newly added child as a reference
    return $parent->lastchild();
 }
 
 

<?xml version="1.0" encoding="ISO-8859-1"?> 
 <guilds> 
   <icon id="####"> 
       <map>???</map> 
       <path>http://blah</path> 
       <x>100</x> 
       <y>100</y> 
   </icon> 
   <icon id="####"> 
       <map>???</map> 
       <path>http://blah2</path> 
       <x>200</x> 
       <y>200</y> 
   </icon> 
 </guilds>