php-doc-en/reference/mongo/mongocollection/group.xml

<?xml version="1.0" encoding="utf-8"?>

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<refentry xml:id="mongocollection.group" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>MongoCollection::group</refname>
  <refpurpose>Performs an operation similar to SQL's GROUP BY command</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <modifier>public</modifier> <type>array</type><methodname>MongoCollection::group</methodname>
   <methodparam><type>array</type><parameter>keys</parameter></methodparam>
   <methodparam><type>array</type><parameter>initial</parameter></methodparam>
   <methodparam><type>string</type><parameter>reduce</parameter></methodparam>
   <methodparam choice="opt"><type>array</type><parameter>condition</parameter><initializer>array()</initializer></methodparam>
  </methodsynopsis>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;  
  <para>
   <variablelist>
    <varlistentry>
     <term>
      <parameter>keys</parameter>
     </term>
     <listitem>
      <para>
       Fields to group by.
      </para>
     </listitem>
    </varlistentry>   
    <varlistentry>
     <term>
      <parameter>initial</parameter>
     </term>
     <listitem>
      <para>
       Initial value of the aggregation counter object.
      </para>
     </listitem>
    </varlistentry>   
    <varlistentry>
     <term>
      <parameter>reduce</parameter>
     </term>
     <listitem>
      <para>
       A function that aggregates (reduces) the objects iterated.
      </para>
     </listitem>
    </varlistentry>   
    <varlistentry>
     <term>
      <parameter>condition</parameter>
     </term>
     <listitem>
      <para>
       An condition that must be true for a row to be considered.
      </para>
     </listitem>
    </varlistentry>   
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns an array containing the result.
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <example>
   <title><function>MongoCollection::group</function> example</title>
   <programlisting role="php">
<![CDATA[
<?php

$collection->save(array("a" => 2));
$collection->save(array("b" => 5));
$collection->save(array("a" => 1));

// use all fields
$keys = array();

// set intial values
$initial = array("count" => 0);

// JavaScript function to perform
$reduce = "function (obj, prev) { prev.count++; }";

// only use documents where the "a" field is greater than 1
$condition = array("a" => array( '$gt' => 1));

$g = $collection->group($keys, $initial, $reduce, $condition);

var_dump($g);

?>
]]>
   </programlisting>
   &example.outputs.similar;
   <screen>
<![CDATA[
array(4) {
  ["retval"]=>
  array(1) {
    [0]=>
    array(1) {
      ["count"]=>
      float(1)
    }
  }
  ["count"]=>
  float(1)
  ["keys"]=>
  int(1)
  ["ok"]=>
  float(1)
}
]]>
   </screen>
  </example>
 </refsect1>

</refentry>
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