PHP 8.1 INTERNALS UPGRADE NOTES

1. Internal API changes
  a. Removed Zend APIs
  b. Zend Stream API
  c. zend_get_opcode_id()
  d. Removed support for "p" printf format specifier
  e. ZEND_ATOL() changes
  f. Non-serializable classes should use ZEND_ACC_NOT_SERIALIZABLE
  g. _zend_hash_find_known_hash renamed to zend_hash_find_known_hash
  h. Renaming of ZEND_TYPE_HAS_CLASS() into ZEND_TYPE_IS_COMPLEX()
  i. zend_resource handle is now zend_long

2. Build system changes
  a. New compiler flags

3. Module changes
  a. ext/hash
  b. ext/pdo
  c. ext/standard
  d. ext/pgsql
  e. ext/pcre

========================
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.
     - The ZVAL_NEW_ARR() macro has been removed. Use array_init() or ZVAL_ARR
       with zend_new_array() instead.
     - The IGNORE_URL_WIN macro has been removed; it had no effect as of PHP 5.0.0.
     - TsHashTable has been removed, it was not used in php-src and was not useful outside of php-src.
  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*
  c. Added the zend_get_opcode_id() function, which is intended to get opcode id from name.
  d. Removed support for "p" modifier (%pd, %pu, etc) in PHP's printf
     implementations. Use ZEND_LONG_FMT and ZEND_ULONG_FMT instead.
  e. ZEND_ATOL() now returns the integer instead of assigning it as part of the
     macro. Replace ZEND_ATOL(i, s) with i = ZEND_ATOL(s).
  f. Non-serializable classes should be indicated using the
     ZEND_ACC_NOT_SERIALIZABLE (@not-serializable in stubs) rather than the
     zend_class_(un)serialize_deny handlers which are removed.
  g. _zend_hash_find_known_hash has been renamed to zend_hash_find_known_hash.
  h. ZEND_TYPE_HAS_CLASS() has been renamed to ZEND_TYPE_IS_COMPLEX() for clarity.
     A zend_type element can contain a zend_type_list which might be either a union or an intersection,
     or a single class stored as either a zend_string* or a zend_class_entry*.
  i. The handle member of zend_resource (the resource ID) now has type zend_long
     rather than int. This should be transparent to most code, but uses in
     printf may need to switch from "%d" to ZEND_LONG_FMT.

========================
2. Build system changes
========================
  a. New compiler flags
     - [-Wimplicit-fallthrough=1] is now enabled by default.
       It is possible to use the new ZEND_FALLTHROUGH macro keyword to suppress the warning.
========================
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().

  c. ext/standard
    - The PHP API php_fputcsv() now takes an extra zend_string* argument at the end
      for a custom EOL sequence, passing NULL provides the old default of "\n".

  d. ext/pgsql
    - The functions php_pgsql_meta_data(), php_pgsql_convert(), php_pgsql_insert(),
      php_pgsql_update(), php_pgsql_delete(), and php_pgsql_select() have had
      their return type formalized to zend_result.
    - The functions php_pgsql_meta_data(), php_pgsql_convert(), php_pgsql_insert(),
      php_pgsql_update(), php_pgsql_delete(), and php_pgsql_select() now accept a
      zend_string* instead of a char* for the table name.

  e. ext/pcre
    - Bundled PCRE2 is at version 10.37. The most important diff to the previous
      version is the JIT support on the S390 platform.