Example of PHP query MongoDB database record ID number

Using Gridfs file to MongoDB, return a Mongoid object, usually we need to save the $id value in this object in a string form to the database, as the identity of the file, then how does PHP take out the ID string value of the Mongoid object?

Find specific records in MongoDB in PHP via _id:

Query conditions need to be written like this: Array ("_id" =>new mongoid ("$id")

This mongoid is shaped like this:

Object (mongoid) #23 (1) {
["$id"] => string (558A7DAB988D4D10140058B1)
}

We want to use PHP to take out ["$id"] value, the problem is that the key name is this form, with $re-> $id definitely wrong, so this value:

Store uploaded Excel to MongoDB
Public Function Savetomongo ($file) {
$id = $this->getgridfs ()->storefile ($file);
return $id->{' $id '};
}

That's OK.