Mention we populate the _id field with the pregenerated ID

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@328551 c90b9560-bf6c-de11-be94-00142212c4b1

reference/mongo/mongocollection/save.xml

@@ -124,6 +124,7 @@ $obj = array('x' => 1);
 
 // insert $obj into the db
 $collection->save($obj);
+var_dump($obj);
 
 // add another field
 $obj['foo'] = 'bar';
@@ -137,9 +138,34 @@ $collection->save($obj);
 ?>
 ]]>
    </programlisting>
+   &example.outputs.similar;
+   <screen>
+<![CDATA[
+array(2) {
+  ["x"]=>
+  int(1)
+  ["_id"]=>
+  object(MongoId)#4 (1) {
+    ["$id"]=>
+    string(24) "50b6afe544415ed606000000"
+  }
+}
+]]>
+   </screen>
   </example>
  </refsect1>
 
+ <refsect1 role="notes"><!-- {{{ -->
+  &reftitle.notes;
+  <note>
+   <para>
+    This method will create an <literal>_id</literal> field in the
+    <parameter>a</parameter> array with a pregenerated ID if the field didn't
+    exist already - unless the argument was a reference.
+   </para>
+  </note>
+ </refsect1><!-- }}} -->
+
 </refentry>
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