Laravel 4，PHP将每个Hashtag保存在一个DB Row中

I am trying to save hashtags to a database. At the moment they are saved in a single row with the image_id and the following format:

Hashtags:    #test bla #test #test

DB:    test,test,test

What do I have to do to save every single hashtag in a single database row maintaining the correstpondig photo_id?

Here is how I save the hashtags:

$hashtag = new Hashtag;

  $hashtag->photo_id = $photo->id;

      $hashtag_string = Input::get('hashtags');




        $str = $hashtag_string;

            preg_match_all('/#([^\s]+)/', $str, $matches);

        $hashtags_final = implode(',', $matches[1]);




$hashtag->hashtag = $hashtags_final;
$hashtag->save();

Depending on your needs there is several solutions:

First: you can loop through hashtags and save them with correct image_id. like this:

$hashtag_string = Input::get('hashtags');

preg_match_all('/#([^\s]+)/', $hashtag_string, $matches);

//looping through matched items in your $matches array
foreach($matches as $tag)
{
  $hashtag = new Hashtag();
  $hashtag->image_id = $photo->id;
  $hashtag->hashtag = $tag;
  $hashtag->save();
}

Second: create Many-to-Many type of relation between Image and Hashtag and use full power of it. You can find everything in the oficial docs on creating and using