Php/docs/xhprof.configuration

From Get docs

Runtime Configuration

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

Xhprof Configure Options
Name Default Changeable Changelog
xhprof.output_dir "" PHP_INI_ALL  

Here's a short explanation of the configuration directives.

xhprof.output_dir string
Directory used by the default implementation of the iXHProfRuns interface (namely, the XHProfRuns_Default class) for storing XHProf runs.