# Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

`MB_OVERLOAD_MAIL` (integer)
`MB_OVERLOAD_STRING` (integer)
`MB_OVERLOAD_REGEX` (integer)
`MB_CASE_UPPER` (integer)
`MB_CASE_LOWER` (integer)
`MB_CASE_TITLE` (integer)
`MB_CASE_FOLD` (integer)
  Available since PHP 7.3.
`MB_CASE_LOWER_SIMPLE` (integer)
  Available since PHP 7.3.
`MB_CASE_UPPER_SIMPLE` (integer)
  Available since PHP 7.3.
`MB_CASE_TITLE_SIMPLE` (integer)
  Available since PHP 7.3.
`MB_CASE_FOLD_SIMPLE` (integer)
  Used by case-insensitive operations. Available since PHP 7.3.
`MB_ONIGURUMA_VERSION` (string)
  The Oniguruma version, e.g. 6.9.4. Available since PHP 7.4.