Sadness

Movie Textures are not supported on iOS. Instead, full-screen streaming playback is provided using Handheld.PlayFullScreenMovie.
http://docs.unity3d.com/Manual/class-MovieTexture.html

Anyway, I solved how to code for playing a movie on the iPhone.

you could add a component to any object in a scene. In my case, I just added a C# script component(movieplayer) to the Main Camera.
Also, you need to add a movie in the "StreamingAssets" folder in the "Assets" folder as seen in the image below.
Finally, you code like this.

using UnityEngine;
using System.Collections;

public class movieplayer : MonoBehaviour {

	// Use this for initialization
	void Start () {
		Handheld.PlayFullScreenMovie ("file://" + Application.streamingAssetsPath + "/"+"EasyMovieTexture.mp4");
		Debug.Log (Application.streamingAssetsPath);
	}
	
	// Update is called once per frame
	void Update () {
	
	}
}

That's all you need to do before build your iOS app. The sad thing is, however, you cannot make sure whether or not the code works fine unless you actually deploy the app on the iPhone. In the emulator you would see nothing.