.ajax getting returned an empty string.

Question

Hi, I'm having some difficulty getting my $.ajax to work correctly. The function is getting called however it is returning an empty string. I'm fairly new to using $.ajax so I appologize if this is easy. The program works when I run it w/o javascript it just loads a new page with the output. Thanks

Here is the .js

$(document).ready(function() {

$('#submit').click(function(){

var formdata = {
years: $('#years').val(),
rate: $('#rate').val(),
principle: $('#principle').val(),
periods: $('#periods').val(),
continuous: $('#continuous').val()
} 

$.ajax({
url: "http://localhost:8888/CodeIgniter_1.7.2/index.php/timevalueshow/submit",
type: 'POST',
data: formdata,
success: function(data){
 console.log(data);
 $('#replace').replaceWith('<p>'+data+'</p>');

}
});

return false;
});


 });

And here is the .php of the function being called.

 function submit(){

 $years = $this->input->post('years');
 $rate = $this->input->post('rate');
 $principle = $this->input->post('principle');
 $periods = $this->input->post('periods');
 $isCont = $this->input->post('continuous');

    $params = array(
     'years' => $years, 
        'rate' => $rate, 
        'principle' => $principle, 
        'periods' => $periods, 
        'isCont' => $isCont
    );

    $this->load->library('timevalue', $params);

    return $this->timevalue->FVFactor();
}