Error validating columns in Excel file

I am using "maatwebsite/excel" package to import excel files and insert the contents of the files into the database. Now I want to validate the columns before insertion but I am having an error. My validations throws me to an empty page instead of returning to the previous page with the error messages.

This is my controller:

public function bulk_upload(Request $request){
        $method = $request->isMethod('post');
        if($method) {
            if ($request->hasFile('file')) {
                //dd('true');
                Excel::load($request->file('file')->getRealPath(), function ($reader) {
                    //Do
                    $i = 2;
                    foreach ($reader->toArray() as $key => $row) {
                        $i++;
                        $name = $row['name'];
                        $address = $row['address'];
                        $phone = $row['phone'];
                        $sex = $row['sex'];
                        $email = $row['email'];
                        $next_of_kin_phone_number = $row['next_of_kin_phone_number'];
                        $dob = $row['date_of_birth'];
                        //dd($row);
                        //validate compulsory
                        if ($name == "" || $address == "" || $phone == "") {
                            return back()->withErrors("Either patient's name, phone number or address is missing at "."line ".$i);
                            //dd("error");
                        }
                        //sex
                        if (isset($sex)) {
                            if (!is_numeric($sex)) {
                                return back()->withErrors("Wrong format for sex");
                            }
                        }
                        //email
                        if (isset($email)) {
                            $count = Patient::where('email', $email)->count();
                            if ($count > 0) {
                                return back()->withErrors("Email address is already taken!");
                            }
                        }
                        //phone number
                        if (isset($phone)) {
                            if (!is_numeric($phone)) {
                                return back()->withErrors("Phone number must be numbers!");
                            } elseif (strlen($phone) != 11) {
                                return back()->withErrors("Phone number must be 11 digits!");
                            }
                        }
                        //next of kin number
                        if (isset($next_of_kin_phone_number)) {
                            if (!is_numeric($next_of_kin_phone_number)) {
                                return back()->withErrors("Next of Kin Phone number must be numbers!");
                            } elseif (strlen($next_of_kin_phone_number) != 11) {
                                return back()->withErrors("Next of Kin Phone number must be 11 digits!");
                            }
                        }
                        //dob
                        if (isset($dob)) {
                            if (!preg_match("/^(0[1-9]|[1-2][0-9]|3[0-1])-(0[1-9]|1[0-2])-[0-9]{4}$/", $dob)) {
                                return back()->withErrors("Wrong date of birth format!");
                            }
                        }
                    }
                    dd("validated");
                });
            }
        }
    }

View:

 <div class="alert alert-danger">
        <ul style="padding-left: 0px;">
            @foreach($errors->all() as $error)
                <li style="list-style: none"></li>
            @endforeach
        </ul>
    </div>
<form class="" method="post" action="" accept-charset="UTF-8" id="users-form" enctype=multipart/form-data>
                            
                            <div class="row">
                                <div class="col-md-6">
                                    <div class="form-group">
                                        <label for="exampleInputName1">Select File</label>
                                        <input type="file" name="file" id="exampleInputName1" class="form-control">
                                    </div>
                                </div>
                            </div>
                            <div class="row">
                                <div class="col-md-4">
                                    <label for="exampleInputName1"><strong>Download Sample file <a href="">here</a> </strong></label>
                                </div>
                            </div>
                            <br>
                            <button type="submit" class="btn btn-success btn-fw">Submit</button>
                        </form>

Route:

Route::match(['post','get'], 'patients/bulk-upload', 'PatientController@bulk_upload');

via Chebli Mohamed