Datatable - JSON not being shown of size larger than 4KB - php

Question

I am using data table to display data returned by a SQL Server 2008 procedure called in Codeigniter via Ajax($POST). Initially I made a very simple procedure with no input parameters, it only returns a list of JSON objects.
Below are my questions and my Codeigniter function returning JSON, AJAX function and JSON structure returned by my Codeigniter function:
1) JSON not returned for chunk larger than 4KB, it simply converts to HTML:
2) What if one of my procedure returns lets say 5000+ record and i want to display it in data table, is my way of doing it right? Or i should use some other best practices:
Codeigniter Function:
public function executeProc()
{
$sqlsrvr = $this->load->database('test', true);
// Get the input values of the procedure
$arr = array();
parse_str($_POST['str'],$arr);
//get Procedure Name
$procName = $_POST['procName'];
$sp ='exec secondProc';
$query = $sqlsrvr->query($sp);//->result();
$jawad = $query->result_array();
$this->output->set_header('Content-type: application/json');
echo json_encode($jawad);
}
AJAX Function
$(document).on('click','#executeProc',function(e){
$('#demo').html('<table cellpadding="0" cellspacing="0" border="0" class="display" id="example"></table>');
e.preventDefault();
var jawad = $( ".jawad" ).serialize();
$.post('<?=base_url();?>command/executeProc',
{str:jawad,procName:$('#procName').val()},
function(html){
//loading data table on return
$('#example').dataTable( {
"data": html,
"columns": [
{ "data": "AppointmentID" },
{ "data": "FirstName" },
{ "data": "LastName" },
{ "data": "AppointmentDate" }
]
} );
});
});
JSON Sample:
[
{
"AppointmentID": "1",
"FirstName": "Test",
"LastName": "test",
"AppointmentDate": "2013-01-12"
},
{
"AppointmentID": "2",
"FirstName": "dfg",
"LastName": "dfg",
"AppointmentDate": "2013-01-01"
}
]
-----AFTER EDIT------
STRANGE BEHAVIOR(JSON tab converts to HTML for larger records)
FOR 40 records that get displayed on data table
FOR records larger then 40 that don't get displayed on data table