How to check if email exist while typing in MYSQL using jQuery, AJAX and CodeIgniter

I want to validate my form's input with database, so when user type on form's input and contain email already in use or exists it will display an alert and cant submit. I use CodeIgniter framework and jQuery.

I've tried using the code below to check if name exists and this could work. But when I apply it to the other case for email, it doesn't work and display message "The URI you submitted has disallowed characters."

How is the correct way to fix this?

View (kasir_halaman.php) :

<div id="addModal" class="modal fade" role="modal">
        <div class="modal-dialog">
            <div class="modal-content">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal">&times;</button>
                    <h3 class="modal-title"><span class="glyphicon glyphicon-plus"></span> Tambah Kasir</h3>
                </div>
                <div class="modal-body">
                    <form action="<?php echo site_url('admin/kasir/addpetugas'); ?>" method="post" enctype="multipart/form-data">
                        <div class="form-group">
                            <label>Nama</label>
                            <input type="text" id="nama" name="nama" class="form-control" maxlength="100" required>
                        </div>
                        <div class="form-group">
                            <label>E-mail</label>
                            <input type="email" id="email" name="email" class="form-control" maxlength="150" required>
                        </div>
                        <div class="form-group">
                            <label>Kategori</label>
                            <select class="form-control" name="kategoripetugas" required>
                                <option value=""> -- Pilih Kategori -- </option>
                                <option value="1">Admin</option>
                                <option value="2">Kasir</option>
                            </select>
                        </div>
                        <div class="form-group">
                            <label>Password</label>
                            <input type="password" name="password" class="form-control" maxlength="30">
                        </div>
                        <div class="form-group">
                            <label>Ulangi Password</label>
                            <input type="password" name="confirmpassword" class="form-control" maxlength="30">
                        </div>
                        <button type="submit" class="btn btn-primary" style="width:100%;">Tambah</button>
                    </form>
                </div>
            </div>
        </div>
    </div>

Controller (kasir.php) :

public function cekData($table, $field, $data)
{
    $match = $this->Crud->read($table, array($field=>$data), null, null);
    if($match->num_rows() > 0){
        $report = 2;
    }else{
        $report = 1;
    }
    echo $report;
}

public function register_email_exists()
{
    if (array_key_exists('email',$_POST)) {
        if ($this->Crud->email_exists($this->input->post('email')) == TRUE ) {
            echo false;
        } else {
            echo true;
        }
    }
}

Model (Crud.php) :

function email_exists($email)
{
    $this->db->where('email', $email);
    $query = $this->db->get('petugas');
    if( $query->num_rows() > 0 ){ return TRUE; } else { return FALSE; }
}

jQuery AJAX (petugas.js) :

$(document).ready(function(){
var check1=0; var id;
$("#nama").bind("keyup change", function(){
    var nama = $(this).val();
    $.ajax({
        url:'kasir/cekData/petugas/nama/'+nama,
        data:{send:true},
        success:function(data){
            if(data==1){
                $("#report1").text("");
                check1=1;
            }else{
                $("#report1").text("*nama petugas sudah terpakai");
                check1=0;
            }
        }
    });
});

var check2=0;
$("#email").bind("keyup change", function(){
    //var email = $(this).val();
    $.ajax({
        url:'kasir/register_email_exists',
        data:{send:true},
        success:function(data){
            if(data==1){
                $("#report2").text("");
                check2=1;
            }else{
                $("#report2").text("*email sudah terpakai");
                check2=0;
            }
        }
    });
});

var check4=0;
$("#confirmpassword").bind("keyup change", function(){
    var password = $("#password").val();
    var confirmpassword = $(this).val();

    if (password == confirmpassword){
        $("#report4").text("");
        check4=1;
    }else{
        $("#report4").text("*Password tidak sama");
        check4=0;
    }
});

$("#submit").click(function(event){
    if(check1==0){
        event.preventDefault();
    }
    if(check4==0){
        event.preventDefault();
    }
});

});