Not receiving data in php codeigniter when sending ajax post

I'm trying to send data by post using ajax (with codeigniter), I don't know why, but I'm not getting anything...

This is how I send it:

var sendData = $('#formContact').serialize();
$.ajax({
    type: 'POST',
    url: '<?php echo base_url()?>/intranet/update/updateProfile',
    data: sendData,
    dataType: 'json',
    success: function (data) 
    {
        console.log(data);
    },
    error: function (xhr, ajaxOptions, thrownError) {
        alert(xhr.status);
        alert(thrownError);
    }
});

Here is an example of my form:

<form id="formContact" action="update" method="POST">
    <input class="headInput" type="text" name="userName" value="Tito"/>
    <input class="headInput" type="text" name="userLastName" value="Lancreo"/>
    <input class="headInput" type="text" name="phone[]" value="666666"/>
    <input class="headInput" type="text" name="phone[]" value="111111"/>
    <input class="headInput" type="text" name="phone[]" value="222222"/>
</form>

When I debug it I always get 0...

[false, false, Array[0], false, null]

my controller:

$this->load->helper('form');
$this->load->library('form_validation');

//1 way
$ret=$this->input->post();

//2 way        
$return=$this->input->post(NULL, TRUE);

//3 way
$all=$_POST;
json_encode($all);

//4 way
$contact=$this->input->post("userName");

//return everything...
$var[0]=$return;
$var[1]=$contact;
$var[2]=$all;
$var[3]=$ret;
$var[4]=$data;
echo json_encode($var);

How can I fix this?