Get post given tag, inverse many-to-many relationship in Laravel

- Andrés Cruz

En español
Get post given tag, inverse many-to-many relationship in Laravel

Many times it is necessary to obtain the records of a parent entity given the child in a many-to-many relationship; the typical relationship is that we have a many-to-many relationship between posts and tags and we want to obtain the posts that belong to certain tags; to do this, we can make a query like the following:

 Post::whereHas('tags', function($q) {
       $q->where('tag_id', 1);
   
    })->whereHas('tags', function($q) {
       $q->where('tag_id', 4);
   
    })->get();

Or if the tags are dynamic:

$tag_ids=[25,40,30];
    Post::where(function($query)use($tag_ids){
        foreach ($id as $value){
            $query->whereHas('tags',function ($query)use($value){
                $query->where('tag_id',$value);
            });
        }
    })->get();

The post model looks like:

class Post extends Model
{
    public function tags()
    {
        return $this->belongsToMany(Tag::class, 'post_tags', 'post_id', 'tag_id');
    }

}
Andrés Cruz

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