MongoDB: Advanced query on array - php

Question

Suppose I have the following objects in my collection:
{id:'123', tags:['berry', 'apple']}
{id:'456', tags:['salad', 'tomatoe']}
{id:'789', tags:['bread', 'rice']}
My search term is "Strawberry". I want to find all objects, where one of the tags is part of search term. In this case it's the object with id '123', since 'berry' is part of 'Strawberry'.
I wanted to use Regex, like this (I'm using php btw):
$regex = new MongoRegex("/.*berry.*/i");
$results = $mongodb->data->find(array("tags" => array('$in' => array($regex))));
but the problem is that the regex is applied on the tags and not on the search result. So i'd need something like a reverse Regex.
Is a query like this somehow possible? Right now I'm doing it like this:
$search = "Strawberry";
$js = "function() { var i = 0; for (; i < this.tags.length; i++) { if ('".$search."'.indexOf(this.tags[i]) != -1) { return true; } } }";
$results = $mongodb->data->find($js);
That's OK for now, since the dataset isn't very large, but will be slow in the future.
Does anyone have a suggestion? Thanks.
UPDATE:
Sorry if this is still not clear.
My search Term is "Strawberry", not "berry". The php code I posted that contains the Regex was just to show that this is not a solution and does not work.
So again: My search term is "Strawberry" and I want to find all objects, where on of the tags is part of the search term, not the other way around
UPDATE 2:
To make it even clearer, in SQL this would be:
SELECT * FROM data WHERE 'Strawberry' LIKE CONCAT('%', tag, '%')

Answer 1

This query will match strawberry if you have in tags
db.collection.aggregate(
[
{$unwind: "$tags"},
{$match : {tags: /.*berry.*/i }}
]
)
Tested output'
{
"result" : [
{
"_id" : ObjectId("537373c17c3639c32fe515fb"),
"id" : "123",
"tags" : "berry"
},
{
"_id" : ObjectId("537375337c3639c32fe515fe"),
"id" : "789",
"tags" : "strawberry"
}
],
"ok" : 1
}
In terms of PHP,
$result = $mongodb->aggregate(array(
array(
'$unwind' => "$tags",
),
array(
'$match' => array(
'tags' => /.*berry.*/i
),
),
));