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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 327604 $ -->
<refentry xml:id="mongodb.execute" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<refnamediv>
<refname>MongoDB::execute</refname>
<refpurpose>Runs JavaScript code on the database server.</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<modifier>public</modifier> <type>array</type><methodname>MongoDB::execute</methodname>
<methodparam><type>mixed</type><parameter>code</parameter></methodparam>
<methodparam choice="opt"><type>array</type><parameter>args</parameter><initializer>array()</initializer></methodparam>
</methodsynopsis>
<para>
The Mongo database server runs a JavaScript engine. This method allows you
to run arbitary JavaScript on the database. This can be useful if you want
touch a number of collections lightly, or process some results on the
database side to reduce the amount that has to be sent to the client.
</para>
<para>
Running JavaScript in the database takes a write lock, meaning it blocks
other operations. Make sure you consider this before running a long script.
</para>
<para>
This is a wrapper for a database command. This method is basically:
<programlisting role="php">
<![CDATA[
<?php
public function execute($code, $args) {
return $this->command(array('$eval' => $code, 'args' => $args));
}
?>
]]>
</programlisting>
</para>
<para>
MongoDB implies a return statement if you have a single statement on a single
line. This can cause some unintuitive behavior. For example, this returns
"foo":
</para>
<programlisting role="php">
<![CDATA[
<?php
$db->execute('"foo";');
?>
]]>
</programlisting>
<para>
However, these return &null;:
</para>
<programlisting role="php">
<![CDATA[
<?php
$db->execute('"bar"; "foo";'); // more than one statement
$db->execute('db.foo.count(
);'); // more than one line
?>
]]>
</programlisting>
<para>
To avoid surprising behavior, it is best not to depend on MongoDB to decide
what to return, but to explicitly state a return value. In the examples
above, we can change them to:
</para>
<programlisting role="php">
<![CDATA[
<?php
$db->execute('"bar"; return "foo";');
$db->execute('return db.foo.count(
);');
?>
]]>
</programlisting>
<para>
Now the first statement will return "foo" and the second statement will
return a count of the "foo" collection.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term>
<parameter>code</parameter>
</term>
<listitem>
<para>
<classname>MongoCode</classname> or string to execute.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<parameter>args</parameter>
</term>
<listitem>
<para>
Arguments to be passed to <literal>code</literal>.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Returns the result of the evaluation.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<example>
<title>Simple <function>MongoDB::execute</function> example</title>
<programlisting role="php">
<![CDATA[
<?php
$response = $db->execute("function() { return 'Hello, world!'; }");
echo $response['retval'];
?>
]]>
</programlisting>
&example.outputs.similar;
<screen>
Hello, world!
</screen>
</example>
<example>
<title>Parameter <function>MongoDB::execute</function> example</title>
<para>
The optional array of parameters will be passed to the JavaScript function.
</para>
<programlisting role="php">
<![CDATA[
<?php
$response = $db->execute("function(greeting, name) { return greeting+', '+name+'!'; }", array("Good bye", "Joe"));
echo $response['retval'];
?>
]]>
</programlisting>
&example.outputs.similar;
<screen>
Good bye, Joe!
</screen>
</example>
<example>
<title>Scope example</title>
<para>
If a <classname>MongoCode</classname> object is used instead of a string for
the first parameter, a scope can be passed in which the JavaScript will be
executed.
</para>
<programlisting role="php">
<![CDATA[
<?php
$func =
"function(greeting, name) { ".
"return greeting+', '+name+', says '+greeter;".
"}";
$scope = array("greeter" => "Fred");
$code = new MongoCode($func, $scope);
$response = $db->execute($code, array("Goodbye", "Joe"));
echo $response['retval'];
?>
]]>
</programlisting>
&example.outputs.similar;
<screen>
Goodbye, Joe, says Fred
</screen>
</example>
</refsect1>
</refentry>
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