Grammar::parameterize() must be of the type array

Title: Understanding and Resolving the "Grammar::parameterize() must be of the type array" Error for Multiple Select Form Input in Laravel

Body:

You encountered an error while working with a multiple-value input select form in your Laravel application, displaying the message "Argument 1 passed to Illuminate\Database\Grammar::parameterize() must be of the type array, string given," when adding array[] in your View. This issue is primarily caused due to a misconception that Laravel's $request->all(), which gives all input from the request, can be directly passed to Eloquent models to create or update multiple relations.

To address this error, you should follow these steps:

1. Remove array[] from your View's select form attribute. Your form should now look like this:

   phpCopy

   <div class = "form-group {{ $errors->has('approver') ? ' has-error' : '' }}">
   
    <label for = "approver" class = "control-label">Approver:</label>
   
    <select name = "approver" multiple class = "form-control select2-multi">
   
        @foreach ($approver as $list)
            <option value = "{{ $list->id }}">{{ $list->username }}</option>
        @endforeach
   
    </select>
   
    @if ($errors->has('approver'))
        <span class = "help-block">{{ $errors->first('approver') }}</span>
    @endif</li>
   </ol>
   <p></div>

   2. Revise your controller's logic to handle multiple relations correctly:
      a. Modify the controller's code and add {!! Form::close() !!}
      phpCopy

      public function getDocuments()
      {
      $approver = DB::table('users')->where('id', '!=', Auth::id())->get();
      
      return view ('document.create')->with('approver', $approver);
      }</li>
      </ol>
      <p>public function postDocuments(Request $request)<br>{</p>
      <pre><code>$this->validate($request,
      [
          'title' => 'required|regex:/(^[A-Za-z0-9 ]+$)+/|max:255',
          'content' => 'required',
          'category' => 'required',
          'recipient' => 'required',
      ]);     
      
      
      $document = new Document();
      $approve = new Approve();
      $user = Auth::user();
                                  //Request in the form
      $document->title = $request->title;
      $document->content = $request->content;
      $document->category_id = $request->category;
      
      foreach ($approve->all() as $item) {
          $document->sentToApprovers()->sync([$item->id],false);
      }
      
      $document->save();

public function createApprovers($data)<br>{<br>    $approverIds = [];<br>    foreach ($data['approver'] as $listId) {<br>        $approver = Approver::find($listId);<br>        if (empty($approver)) {<br>            throw new \Exception('Invalid approver');<br>        }<br>        array_push($approverIds, $approver->id);<br>    }<br>    return $approverIds;<br>}

public function postDocuments(Request $request)<br>{</p>
<pre><code>$this->validate($request,
[
    'title' => 'required|regex:/(^[A-Za-z0-9 ]+$)+/|max:255',
    'content' => 'required',
    'category' => 'required',
    'recipient' => 'required',
]);     


$document = new Document();
$approve = new Approve();
$user = Auth::user();
                            //Request in the form
$document->title = $request->title;
$document->content = $request->content;
$document->category_id = $request->category;

$approverIds = $this->createApprovers($request->all());

foreach ($approve->all() as $item) {
    $document->sentToApprovers()->sync([$item->id],false);
}

$document->save();