New Global Constants
New INI Configuration Directives
Migrating from PHP 5.1.x to PHP 5.2.x
PHP Manual

## New Class Constants

pdo:

- `PDO::ATTR_DEFAULT_FETCH_MODE`
- `PDO::FETCH_PROPS_LATE`
- `PDO::FETCH_KEY_PAIR` Fetches a 2 column result set into an associated array. (Added in PHP 5.2.3)

spl:

- `CachingIterator::FULL_CACHE`
- `CachingIterator::TOSTRING_USE_INNER`
- `SplFileObject::READ_AHEAD`
- `SplFileObject::READ_CSV`
- `SplFileObject::SKIP_EMPTY`

New Global Constants
New INI Configuration Directives
Migrating from PHP 5.1.x to PHP 5.2.x
PHP Manual