/* The variable http will hold our new XMLHttpRequest object. */
var http_datos = createRequestObject(); 

/* Function called to get the product categories list */
function getDatos(){
	/* Create the request. The first argument to the open function is the method (POST/GET),
		and the second argument is the url... 
		document contains references to all items on the page
		We can reference document.form_category_select.select_category_select and we will
		be referencing the dropdown list. The selectedIndex property will give us the 
		index of the selected item. 
	*/
	http_datos.open('get', 'getDatos.php?action=get_datos&id=' 
			+ document.forma_modelos.select_modelos.options[document.forma_modelos.select_modelos.selectedIndex].text);
	/* Define a function to call once a response has been received. This will be our
		handleProductCategories function that we define below. */
	http_datos.onreadystatechange = handleDatos; 
	/* Send the data. We use something other than null when we are sending using the POST
		method. */
	http_datos.send(null);
}

/* Function called to handle the list that was returned from the internal_request.php file.. */
function handleDatos(){
	/* Make sure that the transaction has finished. The XMLHttpRequest object 
		has a property called readyState with several states:
		0: Uninitialized
		1: Loading
		2: Loaded
		3: Interactive
		4: Finished */
	if(http_datos.readyState == 4){ //Finished loading the response
		/* We have got the response from the server-side script,
			let's see just what it was. using the responseText property of 
			the XMLHttpRequest object. */
		var response = http_datos.responseText;
		/* And now we want to change the product_categories <div> content.
			we do this using an ability to get/change the content of a page element 
			that we can find: innerHTML. */
		document.getElementById('datos_coches').innerHTML = response;
	}
}