Definition:
ZEND_BEGIN_ARG_INFO_EX(arginfo_array_multisort, ZEND_SEND_PREFER_REF, 0, 1)
    ZEND_ARG_INFO(ZEND_SEND_PREFER_REF, arr1) /* ARRAY_INFO(0, arg1, 0) */
    ZEND_ARG_INFO(ZEND_SEND_PREFER_REF, SORT_ASC_or_SORT_DESC)
    ZEND_ARG_INFO(ZEND_SEND_PREFER_REF, SORT_REGULAR_or_SORT_NUMERIC_or_SORT_STRING)
    ZEND_ARG_INFO(ZEND_SEND_PREFER_REF, arr2)
    ZEND_ARG_INFO(ZEND_SEND_PREFER_REF, SORT_ASC_or_SORT_DESC)
    ZEND_ARG_INFO(ZEND_SEND_PREFER_REF, SORT_REGULAR_or_SORT_NUMERIC_or_SORT_STRING)
ZEND_END_ARG_INFO()
In the function list:
    PHP_FE(array_multisort, arginfo_array_multisort)
CLI output:
    Function [ <internal:standard> function array_multisort ] {

      - Parameters [6] {
        Parameter #0 [ <required> &$arr1 ]
        Parameter #1 [ <optional> &$SORT_ASC_or_SORT_DESC ]
        Parameter #2 [ <optional> &$SORT_REGULAR_or_SORT_NUMERIC_or_SORT_STRING ]
        Parameter #3 [ <optional> &$arr2 ]
        Parameter #4 [ <optional> &$SORT_ASC_or_SORT_DESC ]
        Parameter #5 [ <optional> &$SORT_REGULAR_or_SORT_NUMERIC_or_SORT_STRING ]
      }
    }