Portability – Database portability features


Each database management system (DBMS) has its own behaviour. For example, some databases capitalize field names in their output, some lowercase them, while others leave them alone. These quirks make it difficult to port your scripts over to another server type. PEAR MDB2 strives to overcome these differences so your program can switch between DBMSs without any changes.

You control which portability modes are enabled by using the portability configuration option. Configuration options are set via factory() and setOption().

The portability modes are bitwised, so they can be combined using | and removed using ^. See the examples section below on how to do this.

NB: MDB2 portability modes are meant to change the behaviour of the returned values only, not that of the query itself. For instance, if you created your tables quoting the identifiers, remember to use the quoteIdentifier() method in all your queries or you'll get "not found" or "not exists" errors. Also check for the quote_identifier option, if it's false then quoting won't be applied if the check_option is used.

Portability Mode Constants

  • MDB2_PORTABILITY_ALL (default)

    turn on all portability features. this is the default setting.


    Force reporting the number of rows deleted. Some DBMSs don't count the number of rows deleted when performing simple DELETE FROM tablename queries. This mode tricks such DBMSs into telling the count by adding WHERE 1=1 to the end of DELETE queries.


    Convert empty strings values to null in data in and output. Needed because Oracle considers empty strings to be null, while most other DBMSs know the difference between empty and null.


    Makes certain error messages in certain drivers compatible with those from other DBMSs

    Error Code Re-mappings
    Driver Description Old Constant New Constant
    mysql, mysqli unique and primary key constraints MDB2_ERROR_ALREADY_EXISTS MDB2_ERROR_CONSTRAINT
    mysql, mysqli not-null constraints MDB2_ERROR_CONSTRAINT MDB2_ERROR_CONSTRAINT_NOT_NULL


    This removes any qualifiers from keys in associative fetches. Some RDBMS, for example SQLite, will default to use the fully qualified name for a column in assoc fetches if it is qualified in a query.


    Convert names of tables and fields to lower or upper case in all methods. The case depends on the field_case option that may be set to either CASE_LOWER (default) or CASE_UPPER. NB: the case change is applied to the returned values only, not to the field and table names in the query.


    Turn off all portability features


    Enable hack that makes numRows() work in Oracle


    Right trim the data output for all data fetches. This does not apply to drivers for RDBMS that automatically right trim values of fixed length character values, even if they do not right trim value of variable length character values.


Disabling all portability options while connecting

require_once 'MDB2.php';

$dsn 'mysql://user:password@host/database'
$options = array(
'debug'       => 2,
'portability' => MDB2_PORTABILITY_NONE,

$mdb2 =& MDB2::connect($dsn$options);
if (
PEAR::isError($mdb2)) {

Using setOption() to enable portability for lowercasing and trimming

// Once you have a valid MDB2 object named $mdb2...

Using setOption() to enable all portability options except trimming

// Once you have a valid MDB2 object named $mdb2...
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Last updated: Tue, 02 Jun 2009 — Download Documentation
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