PHP和Ajax请求

I'm a total newbie to JavaScript, Ajax and PHP, so please excuse any stupid question I might ask.

I'd like to use a lazy loading TreeView which gets it's node data from a database via PHP. I found a JavaScript control to use and an example to try out, and now I have a question.

To lazy load the data for the expanded tree node I need to fire an Ajax request to a PHP file which gives me the answer as a JSON string. In the example I'm trying out this PHP file only delivers one string (with 'echo'), but what do I have to do if I need to loop through a database recordset. Can I 'echo' every partial answer to my lazy loading treeview as I get it from the database or do I need to collect the complete answer inside the PHP file in a string variable and send it only when it's complete?

I don't think that providing any code is helpful, because I think the question is a general question. Can I answer an Ajax request with partial answers and the answer is complete when the PHP file reached it's end or can I answer an Ajax request with only and exactly one complete answer?

I hope you understand my question.

Thanks for any answer or advice in advance.

If i understand your question correctly this is how you can send request and get json data using ajax and loop through it:

Html:

<input id="button" type="button" value="click">

target.php:

<?php

if(isset($_POST['submit']) and $_POST['submit']=='submit'){

$array=array(
array('name'=>'Rasmus','age'=>'32'),
array('name'=>'Jon','age'=>'43'),
array('name'=>'Lora','age'=>'35')
);

$json=json_encode($array);

echo $json;

}

Javascript:

    $("#button").click(function(){
      $.ajax({
           type: 'POST',
           url: 'target.php',
           data: {submit:'submit'},
           success:function(data) {
                var rdata=$.parseJSON(data);
                $.each(rdata,function(){
                    alert(this['name']+this['age']);
                });
            }
        });
    })