How to get posts that match specified several tags

Hello.

I'm creating a search engine for a blog and I've got a problem with selecting posts based on a given, several tags.

I have following models:
- Post  (posts)
- Tag  (tags)
- PostsTag  (posts_tags)
In Post model there is a hasAndBelongsToMany relationship with Tag model defined.

Let's say I have following posts and tags assigned to them:
- "Raspberry icecream" - with "icecream" tag assigned
- "Pineapple icecream" - with "icecream" and "pineapple" tags assigned
- "Pineapple pie" - with "pineapple" and "pie" tags assigned

What I'm trying to do is select posts that match not only one tag, but all the tags that are specified in a search phrase.
Let's say that I've entered to the search engine following search phrase: "pineapple icecream" .

Now, what I want to achieve is to posts that have "pineapple" tag assigned to them and also have "icecream" tag assigned.
So in search results there is only "Pineapple icecream" displayed, because it is assigned to both search conditions words - pineapple and icecream.

How can I do this?
I tried like that:

$tags=$this->Tag->find('all',array('conditions'=>$cond,'fields'=>array('id')));    //here I get all the tags that match every word in search conditions
if($tags) {
  foreach($tags as $t) {
    $tags_ids[]=$t['Tag']['id'];
  }
  $posts_tags=$this->PostsTag->find('all',array('conditions'=>array('tag_id'=>$tags_ids),'fields'=>array('post_id')));
  if($posts_tags) {
    foreach($posts_tags as $pt) {
      $posts_ids[]=$pt['PostsTag']['post_id'];
    }     
  }
}

and then I do the search for posts based on the $posts_ids condition.

But with this solution, I get in search results all the posts, which have either "icecream" tag or "pineapple" tag. Which does not suit my needs.

Any help will be greatly appreciated.

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