HHVM
Predefined Constants
Installing/Configuring
PHP Manual

# Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

mongodb Configure Options
Name | Default | Changeable | Changelog | Comments
--- | --- | --- | --- | ---
mongodb.debug | "" | PHP_INI_ALL |  | Only available for the PHP driver, and not the HHVM one

Here's a short explanation of the configuration directives.

`mongodb.debug` string

  Store full activity debug log in this directory or stream. The special value "stderr" can be provided to write to STDERR.

  > Note:

  > Not available for HHVM

HHVM
Predefined Constants
Installing/Configuring
PHP Manual