MongoDB allows programmers to save and query for data expressed in all of the basic PHP types, compound types (arrays, associative arrays, and objects), and a half-dozen classes provided by the MongoDB PHP driver (for regular expressions, dates, and other specialized applications).

Booleans and `NULL`

TRUE, FALSE, and NULL can be used as-is.

Numbers

Numbers are distinct from strings in MongoDB: "123" does not match 123. Thus, if you want to make sure numbers are sorted and matched correctly, you must make sure that they are actually saved as numbers.


<?php

$doc = array("a" => 123, "b" => "123");
$collection->insert($doc);

$doc->find(array("a" => 123));   // matches
$doc->find(array("a" => "123")); // doesn't match
$doc->find(array("a" => 123.0)); // matches
$doc->find(array("b" => 123));   // doesn't match
$doc->find(array("b" => "123")); // matches

?>

As noted above, floating point numbers do compare with/match integer numbers as one would expect.

Large Numbers

By default, on a 32-bit system, numbers are sent to the database as 32-bit integers. On a 64-bit system, they are sent as 64-bit integers. For backwards compatibility, all systems deserialize 64-bit integers as floating point numbers. Floating point numbers are not exact. If you need exact values, you must tweak your php.ini settings.

On a 32-bit system, if mongo.long_as_object is set, 64-bit integers will be returns as MongoInt64 objects. The integer will be stored in the value field with perfect precision (as a string). You can also use MongoInt64 to save 64-bit integers on 32-bit machines.

On 64-bit systems, you can either set mongo.long_as_object or set mongo.native_long. mongo.native_long will return 64-bit integers and "normal" PHP integers. You can use MongoInt32 to save 32-bit integers on 64-bit machines.

You should set the mongo.long_as_object and mongo.native_long behavior that you plan to use, even if it is the default behavior (to protect against future changes to the defaults).

Strings

Strings must be UTF-8. Non-UTF-8 strings must either be converted to UTF-8 before being sent to the database or saved as binary data.

Regular expressions can be used to match strings, and are expressed using the MongoRegex class.

Binary Data

Non-UTF-8 strings, images, and any other binary data should be sent to the database using the MongoBinData type.

Dates

Dates can be created using the MongoDate class. They are stored as milliseconds since the epoch.

MongoTimestamp is not for saving dates or timestamps, it is used internally by MongoDB. Unless you are creating a tool that interacts with the internals of replication or sharding, you should use MongoDate, not MongoTimestamp.

Unique Ids

The driver will automatically create an _id field before inserting a document (unless one is specified by the user). This field is an instance of MongoId (called "ObjectId" in most other languages).

These ids are 12 bytes long and composed of:

4 bytes of timestamp

No two records can have the same id if they were inserted at different times.
3 bytes machine id

No two records can have the same id if they were inserted on different machines
2 bytes thread id

No two records can have the same id if they were inserted by different threads running on the same machine.
3 bytes incrementing value

Each time an id is created, a global counter is incremented and used as the increment value of the next id.

Thus, no two records can have the same id unless a single process on a single machine managed to insert 256^3 (over 16 million) documents in one second, overflowing the increment field.

JavaScript

MongoDB comes with a JavaScript engine, so you can embed JavaScript in queries (using a $where clause), send it directly to the database to be executed, and use it to perform aggregations.

For security, use MongoCode's scope field to use PHP variables in JavaScript. Code that does not require external values can either use MongoCode or just be a string. See the section on security for more information about sending JavaScript to the database.

Arrays and Objects

Arrays and objects can also be saved to the database. An array with ascending numeric keys will be saved as a an array, anything else will be saved as an object.


<?php

// $scores will be saved as an array
$scores = array(98, 100, 73, 85);
$collection->insert(array("scores" => $scores));

// $scores will be saved as an object
$scores = array("quiz1" => 98, "midterm" => 100, "quiz2" => 73, "final" => 85);
$collection->insert(array("scores" => $scores));

?>

If you query for these objects using the database shell, they will look like:

> db.students.find()
{ "_id" : ObjectId("4b06beada9ad6390dab17c43"), "scores" : [ 98, 100, 73, 85 ] }
{ "_id" : ObjectId("4b06bebea9ad6390dab17c44"), "scores" : { "quiz1" : 98, "midterm" : 100, "quiz2" : 73, "final" : 85 } }

The database can also save arbitrary PHP objects (although they will be returned as associative arrays). The fields are used for the key/value pairs. For example, a blog post might look like:


<?php

  // the blog post class
  class Post {

  var $author;
  var $content;
  var $comments = array();
  var $date;

  public function __construct($author, $content) {
  $this->author = $author;
$this->content = $content;
    $this->date = new MongoDate();
  }

  public function setTitle($title) {
    $this->title = $title;
  }
}

// create a simple blog post and insert it into the database
$post1 = new Post("Adam", "This is a blog post");

$blog->insert($post1);


// there is nothing restricting the type of the "author" field, so we can make
// it a nested object
$author = array("name" => "Fred", "karma" => 42);
$post2 = new Post($author, "This is another blog post.");

// we create an extra field by setting the title
$post2->setTitle("Second Post");

$blog->insert($post2);

?>

From the database shell, this will look something like:

> db.blog.find()
{ "_id" : ObjectId("4b06c263edb87a281e09dad8"), "author" : "Adam", "content" : "This is a blog post", "comments" : [ ], "date" : "Fri Nov 20 2009 11:22:59 GMT-0500 (EST)" }
{ "_id" : ObjectId("4b06c282edb87a281e09dad9"), "author" : { "name" : "Fred", "karma" : 42 }, "content" : "This is a blog post", "comments" : [ ], "date" : "Fri Nov 20 2009 11:23:30 GMT-0500 (EST)", "title" : "Second Post" }

The driver will not detect reference loops in arrays and objects. For example, this will give a fatal error:


<?php

$collection->insert($GLOBALS);

?>

Fatal error: Nesting level too deep - recursive dependency?

If you need to insert documents that may have recursive dependency, you have to check for it yourself before passing it to the driver.

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Booleans and NULL