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.
Running JavaScript in the database takes a write lock, meaning it blocks other operations. Make sure you consider this before running a long script.
This is a wrapper for the » eval database command. This method is basically:
<?php
public function execute($code, $args) {
return $this->command(array('eval' => $code, 'args' => $args));
}
?>
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":
<?php
$db->execute('"foo";');
?>
However, these return NULL:
<?php
$db->execute('"bar"; "foo";'); // more than one statement
$db->execute('db.foo.count(
);'); // more than one line
?>
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:
<?php
$db->execute('"bar"; return "foo";');
$db->execute('return db.foo.count(
);');
?>
Now the first statement will return "foo" and the second statement will return a count of the "foo" collection.
MongoCode or string to execute.
Arguments to be passed to code.
Returns the result of the evaluation.
The » eval command, which this method invokes, is deprecated in MongoDB 3.0+.
This method has been deprecated as a result of the underlaying » eval command being deprecated in MongoDB 3.0+.
<?php
$response = $db->execute("function() { return 'Hello, world!'; }");
echo $response['retval'];
?>
The above example will output something similar to:
Hello, world!
The optional array of parameters will be passed to the JavaScript function.
<?php
$response = $db->execute("function(greeting, name) { return greeting+', '+name+'!'; }", array("Good bye", "Joe"));
echo $response['retval'];
?>
The above example will output something similar to:
Good bye, Joe!
If a MongoCode object is used instead of a string for the first parameter, a scope can be passed in which the JavaScript will be executed.
<?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'];
?>
The above example will output something similar to:
Goodbye, Joe, says Fred
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