Finding duplicate within multiple serialized arrays

[webdev007]

I am not able to come with a logic for merging multiple serialized arrays

Each serialized array contains any num of tags

I need to avoid in result any tag/tags duplicate that could possibly exists in each other array (I do not seek removing dupes)

I think that starting by merging the serialized arrays could be an option and then using twice flip() to avoid listing the dupes?
but I was not successful with the merging process.
How will you perform the task at hand?
your logic?
Thank you

 

[webdev007]

This is what I came with but resulting in no real progress
the bottom part is only a test search segment
it looks like using or not using array_merge gives the same (non merged) result
which is:
Array ( [0] => Array ( [0] => dddd [1] => asas ) ) Array ( [0] => Array ( [0] => dddd [1] => ffffff ) ) Array ( [0] => Array ( [0] => asas [1] => asas [2] => asasas ) ) Array ( [0] => Array ( [0] => asasas [1] => dddd [2] => ddddd mmmm ) )

why may not I get a correct result, obviously I am wrong somewhere!
$num_tags=$db->num_rows($result_tags);

////// ajax call:
while ($row=$db->fetch_assoc($result_tags))
{
$tags=$row['tags'];
$i_tags=0;

while($i_tags <$num_tags)
{

$tags=mysql_result($result_tags, $i_tags, "tags");
$tags=unserialize($tags);

$tags=array_merge(array($tags)); print_r($tags);

$search="ddddd mmmm";
foreach($tags as $tags)
{
if(in_array($search, $tags)) { echo'OK'; }
}
$i_tags++;
}
}