Platforms abstract query generation and the subtle differences of
the supported database vendors. In most cases you don't need to
interact with the
Doctrine\DBAL\Platforms package a lot, but
there might be certain cases when you are programming database
independent where you want to access the platform to generate
queries for you.
The platform can be accessed from any
instance by calling the
<?php $platform = $conn->getDatabasePlatform();
Each database driver has a platform associated with it by default.
Several drivers also share the same platform, for example PDO\_OCI
and OCI8 share the
Doctrine provides abstraction for different versions of platforms if necessary to represent their specific features and dialects. For example has Microsoft added support for sequences in their 2012 version. Therefore Doctrine offers a separate platform class for this extending the previous 2008 version. The 2008 version adds support for additional data types which in turn don't exist in the previous 2005 version and so on. A list of available platform classes that can be used for each vendor can be found as follows:
MySqlPlatformfor version 5.0 and above.
MySQL57Platformfor version 5.7 (5.7.9 GA) and above.
MySQL80Platformfor version 8.0 (8.0 GA) and above.
OraclePlatformfor all versions.
SQLServerPlatformfor version 2008 and above.
SQLServer2012Platformfor version 2012 and above.
PostgreSqlPlatformfor all versions.
PostgreSQL94Platformfor version 9.4 and above.
PostgreSQL100Platformfor version 10.0 and above.
SQLAnywherePlatformfor version 10 and above.
SQLAnywhere11Platformfor version 11 and above.
SQLAnywhere12Platformfor version 12 and above.
SQLAnywhere16Platformfor version 16 and above.
SqlitePlatformfor all versions.
It is highly encouraged to use the platform class that matches your database vendor and version best. Otherwise it is not guaranteed that the compatibility in terms of SQL dialect and feature support between Doctrine DBAL and the database server will always be given.
If you want to overwrite parts of your platform you can do so when
creating a connection. There is a
platform option you can pass
an instance of the platform you want the connection to use:
<?php $myPlatform = new MyPlatform(); $options = array( 'driver' => 'pdo_sqlite', 'path' => 'database.sqlite', 'platform' => $myPlatform ); $conn = DriverManager::getConnection($options);
This way you can optimize your schema or generated SQL code with features that might not be portable for instance, however are required for your special needs. This can include using triggers or views to simulate features or adding behaviour to existing SQL functions.
Platforms are also responsible to know which database type translates to which PHP Type. This is a very tricky issue across all the different database vendors, for example MySQL BIGINT and Oracle NUMBER should be handled as integer. Doctrine 2 offers a powerful way to abstract the database to php and back conversion, which is described in the next section.