Laraval User Existance Check

UserController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Support\Facades\DB; //must need to add during work with database
use App\Http\Controllers\Controller;

class UserController extends Controller
{
 
     public function store(Request $request)
    {
        //validate the data
       $this->validate($request,array(
            'title' => 'required|max:255',
            'slug' => 'required|alpha_dash|min:5|max:255|unique:posts,slug',
            'body'  => 'required',
            'email'  => 'required'
       ));

       //store in databaes
       $post = new Post; //object of post modal

       $post->title = $request->title;
       $post->slug = $request->slug;
       $post->body = $request->body;
       $post->email = $request->email;

       $user = DB::table('users')->where('email', $post->email)->first(); //return 1 row

       if ($user !== null || $user !== "") {
	       	//save data
	       $post->save(); 
	       //session mesage
	       Session::flash('success','Your data has save successfully');
	       //redirect with success message
	       return redirect()->route('posts.show',$post->id);
       } else {
       		//redirect to create page again
       		return redirect()->route('posts.create');
       }
       
       
    }
}