สอบถามเรื่องการส่งข้อมูล insert ajax ครับผมว่าทำไมไม่เข้าฐานข้อมูลครับ

<form method="post" id="insert-form">
      <label>ฺName</label>
      <input type="text" id="fname" name="fname" class="form-control" required="required" />
      <label>LastName</label>
      <input type="text" id="lname" name="lname" class="form-control" required="required" />
      <label>Email</label>
      <input type="email" id="email" name="email"  class="form-control" required="required" />
      <label>Website</label>
      <input type="url" id="web" name="web" class="form-control" required="required" /><br />

      <input type="submit" id="insert" class="btn btn-success" />
      </form>

<script>
$(document).ready(function() {
	
	$('#insert-form').on('submit',function(e){
		
		e.preventDefault();
		$.ajax({
			url:"<?php echo base_url(); ?>employee/insert_data",
			method:"post",
			
			data:$('#insert-form').serialize(),
			beforeSend:function(){
				$('#insert').val("Insert...");
			},
			success:function(data){
				$('#insert-form')[0].reset();
				$('#addModal').modal('hide');
				
			}
			
			});
		
		});
	
</script>

public function insert_data(){
	
	$this->m->insert_student();
}

public function insert_student(){
		$field = array(
		
			'fname'=> mysqli_real_escape_string($this->input->post($fname)),
			'lname'=> mysqli_real_escape_string($this->input->post($lname)),
			'email'=> mysqli_real_escape_string($this->input->post($email)),
			'web'=>   mysqli_real_escape_string($this->input->post($web))
			);
		$this->db->insert('tableuser', $field);
		if($this->db->affected_rows() > 0){
			return true;
		}else{
			return false;
		}
	}