PHP 8.1 INTERNALS UPGRADE NOTES

1. Internal API changes
  a. Removed Zend APIs
  b. Zend Stream API

2. Build system changes

3. Module changes
  a. ext/hash

========================
1. Internal API changes
========================
  a. The following APIs have been removed from the Zend Engine:
     - The spl_ce_Aggregate, spl_ce_ArrayAccess, spl_ce_Countable, spl_ce_Iterator, spl_ce_Serializable,
       spl_ce_Stringable, spl_ce_Traversable alias class entries have been removed in favor of zend_ce_aggregate,
       zend_ce_arrayaccess, zend_ce_countable, zend_ce_iterator, zend_ce_serializable, zend_ce_stringable,
       zend_ce_traversable.
  b. Zend Stream API has been changed to use "zend_string*" instead of "char*"
      - zend_file_handle.filename now is zend_string*
      - zend_file_handle.free_filename is removed. Now zend_file_handle.filename is always released.
      - added zend_file_handle.primary_script flag. SAPIs should set it for main executed script.
      - added zend_file_handle.in_list flag, which is set when a file_handle is added into CG(open_files)
      - added zend_stream_init_filename_ex() function, that takes filename as zend_string*
      - the "filename" parameter of functons zend_stream_open(), php_stream_open_for_zend_ex() and
        callback zend_stream_open_function() has been removed (it's now passed as a "filename" field of the
        file_handle parameter)
      - in zend_fopen() and zend_resolve_path() callbacks filename now passed as zend_string*
      - file_handles should be destroyed by zend_destroy_file_handle() function (usually in the same function
        the same function where they were created by zend_stream_init_*()). Previously there were two different
        destructors zend_destroy_file_handle() and zend_file_handle_dtor().
      - zend_ini_scanner_globals.filename now is zend_string*

========================
2. Build system changes
========================

========================
3. Module changes
========================

  a. ext/hash
    - The init signatures are extended with an additional `HashTable*`
      argument. The passed HT is to contain the algorithm specific
      configuration. If an algorithm doesn't make use of any additional
      configuration, the argument is to be marked with ZEND_ATTRIBUTE_UNUSED.

  b. ext/pdo
    - The "preparer" callback now accepts a zend_string* instead of
      char* + size_t pair the query string. Similarly, the query_string and
      active_query_string members of pdo_stmt_t are now zend_string*.
    - The way in which drivers provide results has changed: Previously,
      the "describer" callback populated the "pdo_type" member in the
      pdo_column_data structure, and the "get_col" callback then had to return
      pointers to data of appropriate type.

      In PHP 8.1, the "describer" callback no longer determines the pdo_type
      (and this member has been removed from pdo_column_data). Instead, the
      "get_col" callback accepts a zval pointer that may be populated with a
      value of arbitrary type. This gives drivers more flexibility in
      determining result types (e.g. based on whether a specific integer fits
      the PHP integer type) and avoid awkward juggling of temporary buffers.

      As the "describer" no longer determines pdo_type, the "get_column_meta"
      function is now responsible for providing this information for use by
      getColumnMeta(). The type provided here does not need to match the type
      returned by get_col (in fact no corresponding type might exist, e.g. for
      floats). It should be the closest logical equivalent for the column type.
    - The transaction, set_attribute, and preparer handler's return type
      has been formalized to bool instead of int.
    - The check_liveness handler's return type has been formalized to zend_return
      instead of int.
    - The closer, and fetch_error handlers have been voidified.
    - The quoter handler now returns the quoted string as zend_string* instead
      of returning a boolean, and the quoted string as a pair of out params.
      Similarly the unquoted string is now a zend_string* instead of a pair of
      char* and size_t length.
    - The doer handler now accepts a zend_string* instead of char* + size_t
      pair for the SQL statement.
    - The last_id handler now returns a zend_string* instead of returning a
      char* and the length as an out param, and accepts a zend_string* instead
      of char* for the optional sequence/table name.
    - The php_pdo_str_tolower_dup() PDO_API has been removed use zend_str_tolower_dup()
      or zend_string_tolower_ex().