I want to make validation for same user assigned using laravel - laravel

Question

I am a beginner and I am trying to make validation for the user assigned when I assign the same user again when I submit so the error message should be shown, this user is already assigned please help me how to do this? thanks.
Controller
public function adduseraction(REQUEST $request) {
// Users_permissions::where('user_id',$request->userid)->get()-
// >pluck('user_Access_id');
$useradd=$request->get('userid');
$checkid=$request->get('multiusersid');
$array = array();
foreach($checkid as $id){
$array[] = array('user_id'=>$useradd,'user_Access_id'=>$id);
}
$user=Users_permissions::insert($array);
return redirect('admin')->with('success', 'Users has been assigned');
}
html view
<form action="{{route('adduseraction')}}" method="post">
{{ csrf_field() }}
<div class="col-sm-4">
<label>Select User</label>
<select name="userid" class="form-control" id="typeofworkday">
<option>Select User</option>
#foreach($users as $user)
<option value="{{$user->id}}">{{$user->name}}</option>
#endforeach
</select>
</div>
<br> <br> <br>
<div class="card-body">
<label>Select Muliple User or One</label>
<!-- Minimal style -->
<div class="row">
#foreach($users as $user)
<div class="col-sm-2">
<div class="form-check">
<input type="checkbox" id="check" name="multiusersid[]" value="
{{$user->id}}" class="form-check-input" >
<h5 style="position:relative;left:10px;">{{$user->name}}</h5>
</div>
<!-- checkbox -->
</div>
#endforeach
</div>
<!-- /.card-body -->
</div>
<br><br><br><br>
<div class="card-footer">
<button type="submit" name="btnsubmit" class="btn btn-primary col-
md-2 center">Submit</button>
</div>
</form>

Answer 1

Ok you can do something like below
First check does user already exists in the table and if exists return redirect with the error message or else insert the data
public function adduseraction(Request $request) {
$isUserAvailable = Users_permissions::where('user_id',$request->userid)->get()- >pluck('user_Access_id');
//If user already exists
if($isUserAvailable) {
return redirect('admin')->with('error', 'Users has been assigned');
}else{
$useradd=$request->get('userid');
$checkid=$request->get('multiusersid');
$array = array();
foreach($checkid as $id){
$array[] = array('user_id'=>$useradd,'user_Access_id'=>$id);
}
$user=Users_permissions::insert($array);
return redirect('admin')->with('success', 'Users has been assigned');
}
}