I've two columns in contents tables 1. id 2. content

now this is what i'm trying to do

Route::post('save', function()
{
    $editor_content=Input::get('editor_content');
    $rules = array('editor_content' => 'required');
    $validator= Validator::make(Input::all(), $rules);
    if($validator->passes())
    {
        //1. check if id is  submitted?
        //2. if id exists update content table 
        //3. else insert new content
            //create new instance
            $content= new Content;
            // insert the content to content column
            $content->content = $editor_content;
            //save the content
            $content->save();
            // check if content has id
            $id=$content->id;

         return Response::json(array('success' => 'sucessfully saved', 'id' => $id));    
        }
    if($validator->fails())
    {
       return $validator->messages() ; 
    }

    });

i wanted to check if id has been already submit or checked i'm processing the request via ajax, and if id exists i wanted update the content column and if it doesn't i wanted to create new instance how do i do it ?