Predefined Constants

The constants below are always available as part of the PHP 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)