migration51-php-databases-8

  • Migrating from PHP 5.0.x to PHP
    5.1.x
  • Changes in database support

  • Changes in database support
  • Changes in database support

    Changes in database support

    PDO overview

    PHP Data
    Objects (PDO)
    were introduced as a PECL extension under PHP
    5.0, and became part of the core PHP distribution in PHP 5.1.x. The
    PDO extension provides a consistent interface for database access,
    and is used alongside database-specific PDO drivers. Each driver
    may also have database-specific functions of its own, but basic
    data access functionality such as issuing queries and fetching data
    is covered by PDO functions, using the driver named in PDO::__construct().

    Note that the PDO extension, and its drivers, are
    intended to be built as shared extensions. This will enable
    straightforward driver upgrades from PECL, without forcing you to
    rebuild all of PHP.

    At the point of the PHP 5.1.x release, PDO is more
    than ready for widespread testing and could be adopted in most
    situations. However, it is important to understand that PDO and its
    drivers are comparatively young and may be missing certain
    database-specific features; evaluate PDO carefully before you use
    it in new projects.

    Legacy code will generally rely on the pre-existing
    database extensions, which are still maintained.

    Changes in MySQL support

    In PHP 4, MySQL 3 support was built-in. With the
    release of PHP 5.0 there were two MySQL extensions, named ‘mysql’
    and ‘mysqli’, which were designed to support MySQL < 4.1 and
    MySQL 4.1 and up, respectively. With the introduction of PDO, which
    provides a very fast interface to all the database APIs supported
    by PHP, the PDO_MYSQL driver can support any of the current
    versions (MySQL 3, 4 or 5) in PHP code written for PDO, depending
    on the MySQL library version used during compilation. The older
    MySQL extensions remain in place for reasons of back compatibility,
    but are not enabled by default.

    Changes in SQLite support

    In PHP 5.0.x, SQLite 2 support was provided by the
    built-in sqlite extension, which was also available as a PECL
    extension in PHP 4.3 and PHP 4.4. With the introduction of PDO, the
    sqlite extension doubles up to act as a ‘sqlite2’ driver for PDO;
    it is due to this that the sqlite extension in PHP 5.1.x has a
    dependency upon the PDO extension.

    PHP 5.1.x ships with a number of alternative
    interfaces to sqlite:

    The sqlite extension provides the “classic” sqlite
    procedural/OO API that you may have used in prior versions of PHP.
    It also provides the PDO ‘sqlite2’ driver, which allows you to
    access legacy SQLite 2 databases using the PDO API.

    PDO_SQLITE provides the ‘sqlite’ version 3 driver.
    SQLite version 3 is vastly superior to SQLite version 2, but the
    file formats of the two versions are not compatible.

    If your SQLite-based project is already written and
    working against earlier PHP versions, then you can continue to use
    ext/sqlite without problems, but will need to explicitly enable
    both PDO and sqlite. New projects should use PDO and the ‘sqlite’
    (version 3) driver, as this is faster than SQLite 2, has improved
    locking concurrency, and supports both prepared statements and
    binary columns natively.

    You must enable PDO to use the SQLite extension. If
    you want to build the PDO extension as a shared extension, then the
    SQLite extension must also be built shared. The same holds true for
    any extension that provides a PDO driver