MongoCursor::valid
MongoId
Mongo
PHP Manual

# Types

## 目次

- MongoId
- MongoCode
- MongoDate
- MongoRegex
- MongoBinData
- MongoDBRef
- MongoMinKey
- MongoMaxKey
- MongoTimestamp

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).

## Simple Types

The built-in types are:

Type | Description | Size in MongoDB (bytes)
--- | --- | ---
`NULL` | Fairly self-explanatory. | 0
boolean | `TRUE` and `FALSE` | 1
int | Integer values. | 4
float | Double values. | 8
string | Strings of UTF-8 characters. | string length + 1

## 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.

## MongoDB Types

The Mongo PHP driver also defines a few new types to use with the database. See class documentation for details and examples.

Type | Description | Size in MongoDB (bytes)
--- | --- | ---
MongoBinData | Binary data. | Number of bytes in binary data + 5
MongoCode | JavaScript code. | String length of code + object size of scope.
MongoDate | Dates and times. Stored as milliseconds since the epoch. | 8

MongoId

Unique document id:

- 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.

12

MongoMinKey | Always smaller than any other value. | String length of code + object size of scope.
MongoMaxKey | JavaScript code. | Always larger than any other value.
MongoRegex | Regular expressions. | Number of characters in regular expression + number of flags
MongoTimestamp | Sharding timestamp | 8

## Unsupported Types

Types supported by Mongo, but not the PHP driver:

Type | Description | Size in MongoDB (bytes)
--- | --- | ---
long | As PHP does not support 8 byte integers, longs fetched from the database are converted to doubles. Integers will always be saved to the database as 4 byte ints (even on machines that support 8 byte ints) and doubles will be saved as 8 bytes doubles, so there is no way to save a long to the database with the PHP driver. | 8

## BSON

MongoDB uses a storage format called "BSON," Binary Serializable Object Notation, which is similar to JSON but more compact and rich in types. Listed below is the exact byte size of each type (or information required to compute its size, in the case of variable-length types). Keep in mind that these sizes do not include field names. The size of an object can be manually computed, but it may be easier for programmers to call the bson_encode() function and take the length of the resulting string.

An example of manually computing BSON size for saving the object array("x" => null, "y" => 40):

    4 bytes (object size)

    1 byte  (type of "x" field)
    2 bytes ("x" and "\0")
    0 bytes (for null)

    1 byte  (type of "y" field)
    2 bytes ("y" and "\0")
    4 bytes (for an integer)

    1 byte  (end-of-object byte)
    -----------------------
    15 bytes

MongoCursor::valid
MongoId
Mongo
PHP Manual