I'm developing web application using PHP with CodeIgniter MVC framework with a huge real time client-side functionality needs. This is my first time to build large scale of client-side app. So I combine the PHP with a large scale of Javascript modules in one project.

As you already know, MVC framework seperate application modules into Model-View-Controller.

My concern is about View layer.

I could be display the data on the DOM by PHP built-in script tag by load some data on the Controller. Otherwise I could use AJAX to pulled the data -- treat the Controller like a service only -- and display the them by Javascript.

Here is some visualization

I could put the data directly from Controller:

<label>Username</label> <input type="text" id="username" value="<?=$userData['username'];?>"><br />
<label>Date of birth</label> <input type="text" id="dob" value="<?=$userData['dob'];?>"><br />
<label>Address</label> <input type="text" id="address" value="<?=$userData['address'];?>">

Or pull them using AJAX:

$.ajax({
  type: "POST",
  url: config.indexURL + "user",                
  dataType: "json",
  success: function(data) { 
    $('#username').val(data.username);
    $('#dateOfBirth').val(data.dob);
    $('#address').val(data.address);
  }
});

So, which approach is better regarding my application has a complex client-side functionality?

In the other hand, PHP-CI has a default mechanism to put the data directly from Controller, so why using AJAX?