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<title>The MongoDB\Driver\Cursor class</title>
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</div><hr /><div id="class.mongodb-driver-cursor" class="reference">
<h1 class="title">The MongoDB\Driver\Cursor class</h1>
<div class="partintro"><p class="verinfo">(mongodb >=1.0.0)</p>
<div class="section" id="mongodb-driver-cursor.intro">
<h2 class="title">Introduction</h2>
<p class="para">
The <strong class="classname">MongoDB\Driver\Cursor</strong> class encapsulates
the results of a MongoDB command or query and may be returned by
<span class="methodname"><a href="mongodb-driver-manager.executecommand.html" class="methodname">MongoDB\Driver\Manager::executeCommand()</a></span> or
<span class="methodname"><a href="mongodb-driver-manager.executequery.html" class="methodname">MongoDB\Driver\Manager::executeQuery()</a></span>, respectively.
</p>
</div>
<div class="section" id="mongodb-driver-cursor.synopsis">
<h2 class="title">Class synopsis</h2>
<div class="classsynopsis">
<div class="ooclass"></div>
<div class="classsynopsisinfo">
<span class="modifier">final</span>
<span class="ooclass">
<strong class="classname">MongoDB\Driver\Cursor</strong>
</span>
<span class="oointerface">implements
<span class="interfacename"><a href="class.traversable.html" class="interfacename">Traversable</a></span>
</span>
{</div>
<div class="classsynopsisinfo classsynopsisinfo_comment">/* Methods */</div>
<div class="methodsynopsis dc-description">
<span class="modifier">final</span> <span class="modifier">private</span> <span class="methodname"><a href="mongodb-driver-cursor.construct.html" class="methodname">__construct</a></span>
( <span class="methodparam">void</span>
)</div>
<div class="methodsynopsis dc-description">
<span class="modifier">final</span> <span class="modifier">public</span> <span class="type">MongoDB\Driver\CursorId</span> <span class="methodname"><a href="mongodb-driver-cursor.getid.html" class="methodname">getId</a></span>
( <span class="methodparam">void</span>
)</div>
<div class="methodsynopsis dc-description">
<span class="modifier">final</span> <span class="modifier">public</span> <span class="type">MongoDB\Driver\Server</span> <span class="methodname"><a href="mongodb-driver-cursor.getserver.html" class="methodname">getServer</a></span>
( <span class="methodparam">void</span>
)</div>
<div class="methodsynopsis dc-description">
<span class="modifier">final</span> <span class="modifier">public</span> <span class="type">bool</span> <span class="methodname"><a href="mongodb-driver-cursor.isdead.html" class="methodname">isDead</a></span>
( <span class="methodparam">void</span>
)</div>
<div class="methodsynopsis dc-description">
<span class="modifier">final</span> <span class="modifier">public</span> <span class="type">void</span> <span class="methodname"><a href="mongodb-driver-cursor.settypemap.html" class="methodname">setTypeMap</a></span>
( <span class="methodparam"><span class="type">array</span> <code class="parameter">$typemap</code></span>
)</div>
<div class="methodsynopsis dc-description">
<span class="modifier">final</span> <span class="modifier">public</span> <span class="type">array</span> <span class="methodname"><a href="mongodb-driver-cursor.toarray.html" class="methodname">toArray</a></span>
( <span class="methodparam">void</span>
)</div>
}</div>
</div>
<div class="section" id="mongodb-driver-cursor.examples">
<h2 class="title">Examples</h2>
<div class="example" id="example-1722">
<p><strong>Example #1 Reading a result set</strong></p>
<div class="example-contents"><p>
<span class="methodname"><a href="mongodb-driver-manager.executecommand.html" class="methodname">MongoDB\Driver\Manager::executeCommand()</a></span> and
<span class="methodname"><a href="mongodb-driver-manager.executequery.html" class="methodname">MongoDB\Driver\Manager::executeQuery()</a></span> both return
their result(s) as a <strong class="classname">MongoDB\Driver\Cursor</strong> object.
This object can be used to iterate over the result set of the command or
query.
</p></div>
<div class="example-contents"><p>
Because <strong class="classname">MongoDB\Driver\Cursor</strong> implements the
<span class="interfacename"><a href="class.traversable.html" class="interfacename">Traversable</a></span> interface, you can simply
iterate over the result set with
<a href="control-structures.foreach.html" class="link"><em>foreach</em></a>.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$manager </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">Manager</span><span style="color: #007700">();<br /><br /></span><span style="color: #FF8000">/* Insert some documents so that our query returns information */<br /></span><span style="color: #0000BB">$bulkWrite </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">BulkWrite</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$bulkWrite</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">([</span><span style="color: #DD0000">'name' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'Ceres'</span><span style="color: #007700">, </span><span style="color: #DD0000">'size' </span><span style="color: #007700">=> </span><span style="color: #0000BB">946</span><span style="color: #007700">, </span><span style="color: #DD0000">'distance' </span><span style="color: #007700">=> </span><span style="color: #0000BB">2.766</span><span style="color: #007700">]);<br /></span><span style="color: #0000BB">$bulkWrite</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">([</span><span style="color: #DD0000">'name' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'Vesta'</span><span style="color: #007700">, </span><span style="color: #DD0000">'size' </span><span style="color: #007700">=> </span><span style="color: #0000BB">525</span><span style="color: #007700">, </span><span style="color: #DD0000">'distance' </span><span style="color: #007700">=> </span><span style="color: #0000BB">2.362</span><span style="color: #007700">]);<br /></span><span style="color: #0000BB">$manager</span><span style="color: #007700">-></span><span style="color: #0000BB">executeBulkWrite</span><span style="color: #007700">(</span><span style="color: #DD0000">"test.asteroids"</span><span style="color: #007700">, </span><span style="color: #0000BB">$bulkWrite</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* Query for all the items in the collection */<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">Query</span><span style="color: #007700">( [] );<br /><br /></span><span style="color: #FF8000">/* Query the "asteroids" collection of the "test" database */<br /></span><span style="color: #0000BB">$cursor </span><span style="color: #007700">= </span><span style="color: #0000BB">$manager</span><span style="color: #007700">-></span><span style="color: #0000BB">executeQuery</span><span style="color: #007700">(</span><span style="color: #DD0000">"test.asteroids"</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">/* $cursor now contains an object that wraps around the result set. Use<br /> * foreach() to iterate over all the result */<br /></span><span style="color: #007700">foreach(</span><span style="color: #0000BB">$cursor </span><span style="color: #007700">as </span><span style="color: #0000BB">$document</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">print_r</span><span style="color: #007700">(</span><span style="color: #0000BB">$document</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
stdClass Object
(
[_id] => MongoDB\BSON\ObjectId Object
(
[oid] => 5a4cff2f122d3321565d8cc2
)
[name] => Ceres
[size] => 946
[distance] => 2.766
)
stdClass Object
(
[_id] => MongoDB\BSON\ObjectId Object
(
[oid] => 5a4cff2f122d3321565d8cc3
)
[name] => Vesta
[size] => 525
[distance] => 2.362
}
</pre></div>
</div>
</div>
<div class="example" id="example-1723">
<p><strong>Example #2 Reading a result set for a tailable cursor</strong></p>
<div class="example-contents"><p>
<a href="https://docs.mongodb.com/manual/core/tailable-cursors" class="link external">» Tailable cursors</a>
are a special type of MongoDB cursor that allows the client to read some
results and then wait until more documents become available. These cursors
are primarily used with
<a href="https://docs.mongodb.com/manual/core/capped-collections" class="link external">» Capped Collections</a>
and <a href="https://docs.mongodb.com/manual/changeStreams" class="link external">» Change Streams</a>.
</p></div>
<div class="example-contents"><p>
While normal cursors can be iterated once with <em>foreach</em>,
that approach will not work with tailable cursors. When
<em>foreach</em> is used with a tailable cursor, the loop will
stop upon reaching the end of the initial result set. Attempting to
continue iteration on the cursor with a second
<em>foreach</em> would throw an exception, since PHP attempts to
rewind the cursor. Similar to result objects in other database drivers,
cursors in MongoDB only support forward iteration, which means they cannot
be rewound.
</p></div>
<div class="example-contents"><p>
In order to continuously read from a tailable cursor, the Cursor object
must be wrapped with an <a href="class.iteratoriterator.html" class="classname">IteratorIterator</a>. This
allows the application to directly control the cursor's iteration, avoid
inadvertently rewinding the cursor, and decide when to wait for new results
or stop iteration entirely.
</p></div>
<div class="example-contents"><p>
In order to demonstrate a tailable cursor in action, two scripts will be
used: a "producer" and a "consumer". The producer script will create a new
capped collection using the
<a href="https://docs.mongodb.com/manual/reference/command/create" class="link external">» create</a> command
and proceed to insert a new document into that collection each second.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$manager </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">Manager</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$manager</span><span style="color: #007700">-></span><span style="color: #0000BB">executeCommand</span><span style="color: #007700">(</span><span style="color: #DD0000">'test'</span><span style="color: #007700">, new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">Command</span><span style="color: #007700">([<br /> </span><span style="color: #DD0000">'create' </span><span style="color: #007700">=> </span><span style="color: #DD0000">'asteroids'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'capped' </span><span style="color: #007700">=> </span><span style="color: #0000BB">true</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'size' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1048576</span><span style="color: #007700">,<br />]));<br /><br />while (</span><span style="color: #0000BB">true</span><span style="color: #007700">) {<br /> </span><span style="color: #0000BB">$bulkWrite </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">BulkWrite</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$bulkWrite</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">([</span><span style="color: #DD0000">'createdAt' </span><span style="color: #007700">=> new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">BSON</span><span style="color: #007700">\</span><span style="color: #0000BB">UTCDateTime</span><span style="color: #007700">]);<br /> </span><span style="color: #0000BB">$manager</span><span style="color: #007700">-></span><span style="color: #0000BB">executeBulkWrite</span><span style="color: #007700">(</span><span style="color: #DD0000">'test.asteroids'</span><span style="color: #007700">, </span><span style="color: #0000BB">$bulkWrite</span><span style="color: #007700">);<br /><br /> </span><span style="color: #0000BB">sleep</span><span style="color: #007700">(</span><span style="color: #0000BB">1</span><span style="color: #007700">);<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>
With the producer script still running, a second consumer script may be
executed to read the inserted documents using a tailable cursor, indicated
by the <em>tailable</em> and <em>awaitData</em> options
to <span class="function"><a href="mongodb-driver-query.construct.html" class="function">MongoDB\Driver\Query::__construct()</a></span>.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$manager </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">Manager</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= new </span><span style="color: #0000BB">MongoDB</span><span style="color: #007700">\</span><span style="color: #0000BB">Driver</span><span style="color: #007700">\</span><span style="color: #0000BB">Query</span><span style="color: #007700">([], [<br /> </span><span style="color: #DD0000">'tailable' </span><span style="color: #007700">=> </span><span style="color: #0000BB">true</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'awaitData' </span><span style="color: #007700">=> </span><span style="color: #0000BB">true</span><span style="color: #007700">,<br />]);<br /><br /></span><span style="color: #0000BB">$cursor </span><span style="color: #007700">= </span><span style="color: #0000BB">$manager</span><span style="color: #007700">-></span><span style="color: #0000BB">executeQuery</span><span style="color: #007700">(</span><span style="color: #DD0000">'test.asteroids'</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$iterator </span><span style="color: #007700">= new </span><span style="color: #0000BB">IteratorIterator</span><span style="color: #007700">(</span><span style="color: #0000BB">$cursor</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$iterator</span><span style="color: #007700">-></span><span style="color: #0000BB">rewind</span><span style="color: #007700">();<br /><br />while (</span><span style="color: #0000BB">true</span><span style="color: #007700">) {<br /> if (</span><span style="color: #0000BB">$iterator</span><span style="color: #007700">-></span><span style="color: #0000BB">valid</span><span style="color: #007700">()) {<br /> </span><span style="color: #0000BB">$document </span><span style="color: #007700">= </span><span style="color: #0000BB">$iterator</span><span style="color: #007700">-></span><span style="color: #0000BB">current</span><span style="color: #007700">();<br /> </span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"Consumed document created at: %s\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">$document</span><span style="color: #007700">-></span><span style="color: #0000BB">createdAt</span><span style="color: #007700">);<br /> }<br /><br /> </span><span style="color: #0000BB">$iterator</span><span style="color: #007700">-></span><span style="color: #0000BB">next</span><span style="color: #007700">();<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>
The consumer script will start by quickly printing all available documents
in the capped collection (as if <em>foreach</em> had been used);
however, it will not terminate upon reaching the end of the initial result
set. Since the cursor is tailable, calling
<span class="function"><a href="iteratoriterator.next.html" class="function">IteratorIterator::next()</a></span> will block and wait for
additional results. <span class="function"><a href="iteratoriterator.valid.html" class="function">IteratorIterator::valid()</a></span> is also
used to check if there is actually data available to read at each step.
</p></div>
<blockquote class="note"><p><strong class="note">Note</strong>:
<span class="simpara">
This example uses the <em>awaitData</em> query option to
instruct the server to block for a short period (e.g. one second) at the
end of the result set before returning a response to the driver. This is
used to prevent the driver from aggressively polling the server when there
are no results available. The <em>maxAwaitTimeMS</em> option may
be used in conjunction with <em>tailable</em> and
<em>awaitData</em> to specify the amount of time that the server
should block when it reaches the end of the result set.
</span>
</p></blockquote>
</div>
</div>
<div class="section">
<h2 class="title">Errors/Exceptions</h2>
<p class="simpara">
When iterating over the cursor object, BSON data is converted into PHP
variables. This iteration can cause the following Exceptions:
</p>
<ul class="simplelist">
<li class="member">
Throws
<a href="class.mongodb-driver-exception-invalidargumentexception.html" class="classname">MongoDB\Driver\Exception\InvalidArgumentException</a> if
a class in the type map cannot be instantiated or does not implement
<span class="interfacename"><a href="class.mongodb-bson-unserializable.html" class="interfacename">MongoDB\BSON\Unserializable</a></span>.
</li>
<li class="member">Throws <a href="class.mongodb-driver-exception-unexpectedvalueexception.html" class="classname">MongoDB\Driver\Exception\UnexpectedValueException</a> if the input did not contain exactly one BSON document. Possible reasons include, but are not limited to, invalid BSON, extra data (after reading one BSON document), or an unexpected <a href="https://github.com/mongodb/libbson" class="link external">» libbson</a> error.</li>
</ul>
</div>
</div>
<h2>Table of Contents</h2><ul class="chunklist chunklist_reference"><li><a href="mongodb-driver-cursor.construct.html">MongoDB\Driver\Cursor::__construct</a> — Create a new Cursor (not used)</li><li><a href="mongodb-driver-cursor.getid.html">MongoDB\Driver\Cursor::getId</a> — Returns the ID for this cursor</li><li><a href="mongodb-driver-cursor.getserver.html">MongoDB\Driver\Cursor::getServer</a> — Returns the server associated with this cursor</li><li><a href="mongodb-driver-cursor.isdead.html">MongoDB\Driver\Cursor::isDead</a> — Checks if the cursor may have additional results</li><li><a href="mongodb-driver-cursor.settypemap.html">MongoDB\Driver\Cursor::setTypeMap</a> — Sets a type map to use for BSON unserialization</li><li><a href="mongodb-driver-cursor.toarray.html">MongoDB\Driver\Cursor::toArray</a> — Returns an array containing all results for this cursor</li></ul>
</div>
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