where is php.ini in wordpress code example

Example: php ini wordpress

Configuring PHP directives
See the "Configuration" section of the php image documentation.

For example, to adjust common php.ini flags like upload_max_filesize,
you could create a custom.ini with the desired parameters 
  and place it in the $PHP_INI_DIR/conf.d/ directory.

$PHP_INI_DIR/conf.d/