Roll a Ball tutorial

I am trying to do the roll a ball tutorial and when i write the script word for word like the tutorial I get the error...

"The class defined in script file named 'PlayerController' does not match file name!"

this is my code

 using UnityEngine;
 using System.Collections;
 
 public class PlayerController : MonoBehaviour
 
 {
             void fixedupdate()
         {
             float moveHorizontal = Input.GetAxis ("Horizontal");
             float moveVertical = Input.GetAxis ("Vertical");
             
             Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
             rigidbody.AddForce (movement);
         }
     }

please help Thanks