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<h1 class="refname">MongoCollection::group</h1>
<p class="verinfo">(PECL mongo >=0.9.2)</p><p class="refpurpose"><span class="refname">MongoCollection::group</span> — <span class="dc-title">Performs an operation similar to SQL's GROUP BY command</span></p>
</div>
<div class="refsect1 description" id="refsect1-mongocollection.group-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="modifier">public</span> <span class="type">array</span> <span class="methodname"><strong>MongoCollection::group</strong></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$keys</code></span>
, <span class="methodparam"><span class="type">array</span> <code class="parameter">$initial</code></span>
, <span class="methodparam"><span class="type"><a href="class.mongocode.html" class="type MongoCode">MongoCode</a></span> <code class="parameter">$reduce</code></span>
[, <span class="methodparam"><span class="type">array</span> <code class="parameter">$options</code><span class="initializer"> = array()</span></span>
] )</div>
</div>
<div class="refsect1 parameters" id="refsect1-mongocollection.group-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term">
<em><code class="parameter">keys</code></em>
</span>
<dd>
<p class="para">
Fields to group by. If an array or non-code object is passed, it will be
the key used to group results.
</p>
<p class="para">1.0.4+: If <em><code class="parameter">keys</code></em> is an instance of
<a href="class.mongocode.html" class="classname">MongoCode</a>, <em><code class="parameter">keys</code></em> will be treated as
a function that returns the key to group by (see the "Passing a
<em><code class="parameter">keys</code></em> function" example below).
</p>
</dd>
</dt>
<dt>
<span class="term">
<em><code class="parameter">initial</code></em>
</span>
<dd>
<p class="para">
Initial value of the aggregation counter object.
</p>
</dd>
</dt>
<dt>
<span class="term">
<em><code class="parameter">reduce</code></em>
</span>
<dd>
<p class="para">
A function that takes two arguments (the current document and the
aggregation to this point) and does the aggregation.
</p>
</dd>
</dt>
<dt>
<span class="term">
<em><code class="parameter">options</code></em>
</span>
<dd>
<p class="para">
Optional parameters to the group command. Valid options include:
</p>
<ul class="itemizedlist">
<li class="listitem">
<p class="para">
<em>"condition"</em>
</p>
<p class="para">
Criteria for including a document in the aggregation.
</p>
</li>
<li class="listitem">
<p class="para">
<em>"finalize"</em>
</p>
<p class="para">
Function called once per unique key that takes the final output of the
reduce function.
</p>
</li>
</ul>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-mongocollection.group-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns an array containing the result.
</p>
</div>
<div class="refsect1 changelog" id="refsect1-mongocollection.group-changelog">
<h3 class="title">Changelog</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>Version</th>
<th>Description</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>1.2.11</td>
<td>
Emits <strong><code>E_DEPRECATED</code></strong> when
<em><code class="parameter">options</code></em> is <span class="type"><span class="type scalar">scalar</span></span>.
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-mongocollection.group-examples">
<h3 class="title">Examples</h3>
<div class="example" id="example-1459">
<p><strong>Example #1 <span class="function"><strong>MongoCollection::group()</strong></span> example</strong></p>
<div class="example-contents"><p>
This groups documents by category and creates a list of names within that
category.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"category" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"fruit"</span><span style="color: #007700">, </span><span style="color: #DD0000">"name" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"apple"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"category" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"fruit"</span><span style="color: #007700">, </span><span style="color: #DD0000">"name" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"peach"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"category" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"fruit"</span><span style="color: #007700">, </span><span style="color: #DD0000">"name" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"banana"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"category" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"veggie"</span><span style="color: #007700">, </span><span style="color: #DD0000">"name" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"corn"</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">insert</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"category" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"veggie"</span><span style="color: #007700">, </span><span style="color: #DD0000">"name" </span><span style="color: #007700">=> </span><span style="color: #DD0000">"broccoli"</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">$keys </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"category" </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$initial </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"items" </span><span style="color: #007700">=> array());<br /><br /></span><span style="color: #0000BB">$reduce </span><span style="color: #007700">= </span><span style="color: #DD0000">"function (obj, prev) { prev.items.push(obj.name); }"</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$g </span><span style="color: #007700">= </span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">group</span><span style="color: #007700">(</span><span style="color: #0000BB">$keys</span><span style="color: #007700">, </span><span style="color: #0000BB">$initial</span><span style="color: #007700">, </span><span style="color: #0000BB">$reduce</span><span style="color: #007700">);<br /><br />echo </span><span style="color: #0000BB">json_encode</span><span style="color: #007700">(</span><span style="color: #0000BB">$g</span><span style="color: #007700">[</span><span style="color: #DD0000">'retval'</span><span style="color: #007700">]);<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>
[{"category":"fruit","items":["apple","peach","banana"]},{"category":"veggie","items":["corn","broccoli"]}]
</pre></div>
</div>
</div>
<div class="example" id="example-1460">
<p><strong>Example #2 <span class="function"><strong>MongoCollection::group()</strong></span> example</strong></p>
<div class="example-contents"><p>
This example doesn't use any key, so every document will be its own group.
It also uses a condition: only documents that match this condition will be
processed by the grouping function.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">save</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"a" </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">save</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"b" </span><span style="color: #007700">=> </span><span style="color: #0000BB">5</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">save</span><span style="color: #007700">(array(</span><span style="color: #DD0000">"a" </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">// use all fields<br /></span><span style="color: #0000BB">$keys </span><span style="color: #007700">= array();<br /><br /></span><span style="color: #FF8000">// set intial values<br /></span><span style="color: #0000BB">$initial </span><span style="color: #007700">= array(</span><span style="color: #DD0000">"count" </span><span style="color: #007700">=> </span><span style="color: #0000BB">0</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// JavaScript function to perform<br /></span><span style="color: #0000BB">$reduce </span><span style="color: #007700">= </span><span style="color: #DD0000">"function (obj, prev) { prev.count++; }"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">// only use documents where the "a" field is greater than 1<br /></span><span style="color: #0000BB">$condition </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'condition' </span><span style="color: #007700">=> array(</span><span style="color: #DD0000">"a" </span><span style="color: #007700">=> array( </span><span style="color: #DD0000">'$gt' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">)));<br /><br /></span><span style="color: #0000BB">$g </span><span style="color: #007700">= </span><span style="color: #0000BB">$collection</span><span style="color: #007700">-></span><span style="color: #0000BB">group</span><span style="color: #007700">(</span><span style="color: #0000BB">$keys</span><span style="color: #007700">, </span><span style="color: #0000BB">$initial</span><span style="color: #007700">, </span><span style="color: #0000BB">$reduce</span><span style="color: #007700">, </span><span style="color: #0000BB">$condition</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$g</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(4) {
["retval"]=>
array(1) {
[0]=>
array(1) {
["count"]=>
float(1)
}
}
["count"]=>
float(1)
["keys"]=>
int(1)
["ok"]=>
float(1)
}
</pre></div>
</div>
</div>
<div class="example" id="example-1461">
<p><strong>Example #3 Passing a <em><code class="parameter">keys</code></em> function</strong></p>
<div class="example-contents"><p>
If you want to group by something other than a field name, you can pass
a function as the first parameter of
<span class="function"><strong>MongoCollection::group()</strong></span> and it will be run against each
document. The return value of the function will be used as its grouping
value.
</p></div>
<div class="example-contents"><p>
This example demonstrates grouping by the num field modulo 4.
</p></div>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$c</span><span style="color: #007700">-></span><span style="color: #0000BB">group</span><span style="color: #007700">(new </span><span style="color: #0000BB">MongoCode</span><span style="color: #007700">(</span><span style="color: #DD0000">'function(doc) { return {mod : doc.num % 4}; }'</span><span style="color: #007700">),<br /> array(</span><span style="color: #DD0000">"count" </span><span style="color: #007700">=> </span><span style="color: #0000BB">0</span><span style="color: #007700">),<br /> new </span><span style="color: #0000BB">MongoCode</span><span style="color: #007700">(</span><span style="color: #DD0000">'function(current, total) { total.count++; }'</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</div>
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