Suppose we wish to change the name of a comment's author in this document:
{
"_id" : ObjectId("4b06c282edb87a281e09dad9"),
"content" : "this is a blog post.",
"comments" :
[
{
"author" : "Mike",
"comment" : "I think that blah blah blah...",
},
{
"author" : "John",
"comment" : "I disagree."
}
]
}
<?php
$blog->update($criteria, array('$set' => array("comments.1" => array("author" => "Jim"))));
?>
The positional operator $ is useful for updating objects that are in arrays. In the example above, for instance, suppose that we did not know the index of the comment that we needed to change, merely that we needed to change "John" to "Jim". We can use $ to do so.
<?php
$blog->update(
array('comments.author' => 'John'),
array('$set' => array('comments.$.author' => 'Jim')));
?>