PHP 8.1 INTERNALS UPGRADE NOTES

1. Internal API changes

2. Build system changes

3. Module changes
  a. ext/hash

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1. Internal API changes
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2. Build system changes
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3. Module changes
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  a. ext/hash
    - The init signatures are extended with an additional `HashTable*`
      argument. The passed HT is to contain the algorithm specific
      configuration. If the 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.