&reftitle.constants; &extension.constants.core;

`CASE_LOWER` (`int`)

- `CASE_LOWER` is used with `array_change_key_case` and is used to convert array keys to lower case. This is also the default case for `array_change_key_case`. As of PHP 8.2.0, only ASCII characters will be converted.

`CASE_UPPER` (`int`)

- `CASE_UPPER` is used with `array_change_key_case` and is used to convert array keys to upper case. As of PHP 8.2.0, only ASCII characters will be converted.

Sorting order flags:

`SORT_ASC` (`int`)

- `SORT_ASC` is used with `array_multisort` to sort in ascending order.

`SORT_DESC` (`int`)

- `SORT_DESC` is used with `array_multisort` to sort in descending order.

Sorting type flags: used by various sort functions

`SORT_REGULAR` (`int`)

- `SORT_REGULAR` is used to compare items normally.

`SORT_NUMERIC` (`int`)

- `SORT_NUMERIC` is used to compare items numerically.

`SORT_STRING` (`int`)

- `SORT_STRING` is used to compare items as strings.

`SORT_LOCALE_STRING` (`int`)

- `SORT_LOCALE_STRING` is used to compare items as strings, based on the current locale.

`SORT_NATURAL` (`int`)

- `SORT_NATURAL` is used to compare items as strings using "natural ordering" like `natsort`.

`SORT_FLAG_CASE` (`int`)

- `SORT_FLAG_CASE` can be combined (bitwise OR) with `SORT_STRING` or `SORT_NATURAL` to sort strings case-insensitively. As of PHP 8.2.0, only ASCII case folding will be done.

Filter flags:

`ARRAY_FILTER_USE_KEY` (`int`)

- `ARRAY_FILTER_USE_KEY` is used with `array_filter` to pass each key as the first argument to the given callback function.

`ARRAY_FILTER_USE_BOTH` (`int`)

- `ARRAY_FILTER_USE_BOTH` is used with `array_filter` to pass both value and key to the given callback function.

`COUNT_NORMAL` (`int`)

`COUNT_RECURSIVE` (`int`)

`EXTR_OVERWRITE` (`int`)

`EXTR_SKIP` (`int`)

`EXTR_PREFIX_SAME` (`int`)

`EXTR_PREFIX_ALL` (`int`)

`EXTR_PREFIX_INVALID` (`int`)

`EXTR_PREFIX_IF_EXISTS` (`int`)

`EXTR_IF_EXISTS` (`int`)

`EXTR_REFS` (`int`)