MongoCollection::validate
MongoCursor::addOption
Core Classes
PHP Manual

# The MongoCursor class

(PECL mongo >=0.9.0)

## Introduction

A cursor is used to iterate through the results of a database query. For example, to query the database and see all results, you could do:

Example #1 MongoCursor basic usage

`<?php
$cursor = $collection->find();
var_dump(iterator_to_array($cursor));
?>`

You don't generally create cursors using the MongoCursor constructor, you get a new cursor by calling MongoCollection::find() (as shown above).

Suppose that, in the example above, $collection was a 50GB collection. We certainly wouldn't want to load that into memory all at once, which is what a cursor is for: allowing the client to access the collection in dribs and drabs.

If we have a large result set, we can iterate through it, loading a few megabytes of results into memory at a time. For example, we could do:

Example #2 Iterating over MongoCursor

`<?php
$cursor = $collection->find();
foreach ($cursor as $doc) {
// do something to each document
}
?>`
This will go through each document in the collection, loading and garbage collecting documents as needed.

Note that this means that a cursor does not "contain" the database results, it just manages them. Thus, if you print a cursor (with, say, var_dump() or print_r()), you'll just get the cursor object, not your documents. To get the documents themselves, you can use one of the methods shown above.

## Cursor Stages

A MongoCursor has two "life stages": pre- and post- query. When a cursor is created, it has not yet contacted the database, so it is in its pre-query state. In this state, the client can further specify what they want the query to do, including adding limits, skips, sorts, and more advanced options.

When the client attempts to get a result (by calling MongoCursor::next(), directly or indirectly), the cursor moves into the post-query stage. At this point, the query has been executed by the database and cannot be modified anymore.

Example #3 Adding options to MongoCursor

`<?php
$cursor = $collection->find()->limit(10);
// database has not yet been queried, so more search options can be added
$cursor = $cursor->sort(array("a" => 1));
var_dump($cursor->getNext());
// now database has been queried and more options cannot be added
// so this will throw an exception:
$cursor->skip(4);
?>`

## Class synopsis

MongoCursor implements Iterator {
/* Static Fields */
static boolean $slaveOkay = `FALSE` ;
static integer $timeout = 30000 ;
/* Methods */
public MongoCursor addOption ( string `$key` , mixed `$value` )
public MongoCursor awaitData ([ bool `$wait` = true ] )
public MongoCursor batchSize ( int `$batchSize` )
public __construct ( MongoClient `$connection` , string `$ns` [, array `$query` = array() [, array `$fields` = array() ]] )
public int count ([ bool `$foundOnly` = `FALSE` ] )
public array current ( void )
public bool dead ( void )
protected void doQuery ( void )
public array explain ( void )
public MongoCursor fields ( array `$f` )
public array getNext ( void )
public array getReadPreference ( void )
public bool hasNext ( void )
public MongoCursor hint ( mixed `$index` )
public MongoCursor immortal ([ bool `$liveForever` = true ] )
public array info ( void )
public string key ( void )
public MongoCursor limit ( int `$num` )
public void next ( void )
public MongoCursor partial ([ bool `$okay` = true ] )
public void reset ( void )
public void rewind ( void )
public MongoCursor setFlag ( int `$flag` [, bool `$set` = true ] )
public MongoCursor setReadPreference ( string `$read_preference` [, array `$tags` ] )
public MongoCursor skip ( int `$num` )
public MongoCursor slaveOkay ([ bool `$okay` = true ] )
public MongoCursor snapshot ( void )
public MongoCursor sort ( array `$fields` )
public MongoCursor tailable ([ bool `$tail` = true ] )
public MongoCursor timeout ( int `$ms` )
public bool valid ( void )
}

## Static Variables

slaveOkay

  If the query should have the "slaveOkay" flag set, which allows reads on the secondary (secondaries are, by default, just for backup and not queried). Can be overridden with MongoCursor::slaveOkay().

  This functionality is deprecated. Please use Read Preferences instead.

timeout

  Set timeout in milliseconds for all database responses. Use -1 to wait forever. Can be overridden with MongoCursor::timeout(). This does not cause the MongoDB server to cancel the operation; it only instructs the driver to stop waiting for a response and throw a MongoCursorTimeoutException after a set time.

## See Also

MongoDB core docs on » cursors.

## Table of Contents

- MongoCursor::addOption — Adds a top-level key/value pair to a query
- MongoCursor::awaitData — Sets whether this cursor will wait for a while for a tailable cursor to return more data
- MongoCursor::batchSize — Limits the number of elements returned in one batch.
- MongoCursor::__construct — Create a new cursor
- MongoCursor::count — Counts the number of results for this query
- MongoCursor::current — Returns the current element
- MongoCursor::dead — Checks if there are documents that have not been sent yet from the database for this cursor
- MongoCursor::doQuery — Execute the query.
- MongoCursor::explain — Return an explanation of the query, often useful for optimization and debugging
- MongoCursor::fields — Sets the fields for a query
- MongoCursor::getNext — Return the next object to which this cursor points, and advance the cursor
- MongoCursor::getReadPreference — Get the read preference for this query
- MongoCursor::hasNext — Checks if there are any more elements in this cursor
- MongoCursor::hint — Gives the database a hint about the query
- MongoCursor::immortal — Sets whether this cursor will timeout
- MongoCursor::info — Gets the query, fields, limit, and skip for this cursor
- MongoCursor::key — Returns the current result's _id
- MongoCursor::limit — Limits the number of results returned
- MongoCursor::next — Advances the cursor to the next result
- MongoCursor::partial — If this query should fetch partial results from mongos if a shard is down
- MongoCursor::reset — Clears the cursor
- MongoCursor::rewind — Returns the cursor to the beginning of the result set
- MongoCursor::setFlag — Sets arbitrary flags in case there is no method available the specific flag
- MongoCursor::setReadPreference — Set the read preference for this query
- MongoCursor::skip — Skips a number of results
- MongoCursor::slaveOkay — Sets whether this query can be done on a secondary
- MongoCursor::snapshot — Use snapshot mode for the query
- MongoCursor::sort — Sorts the results by given fields
- MongoCursor::tailable — Sets whether this cursor will be left open after fetching the last results
- MongoCursor::timeout — Sets a client-side timeout for this query
- MongoCursor::valid — Checks if the cursor is reading a valid result.

MongoCollection::validate
MongoCursor::addOption
Core Classes
PHP Manual