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.