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Connecting

Connecting -- Connecting and disconnecting a database

Описание

To instantiate a database object you have several methods available using MDB2.

Таблица 35-1. Connection functions

Function	Summary	Description
factory()	Efficient	Will instantiate a new MDB2_Driver_Common instance, but will not connect to the database until required. This will delay making the actual connection. This is called lazy connecting. Using this makes sense if it is possible that due to caching inside the application no connection will ever need to be established.
connect()	Eager	Will instantiate a new MDB2_Driver_Common instance, and will establish a database connection immediately. This way any connection issues will immediately raise an error.
singleton()	Available	Returns a MDB2_Driver_Common instance. A new MDB2_Driver_Common object is only created once using factory(), subsequent calls to singleton will return a reference to the existing object. This method is preferred over declaring your database object as a global.

To connect to a database you have to use the function factory(), connect() or singleton(), which require a valid DSN as the first parameter. This parameter can either be a string or an array. If using an array, the array used gets merged with the default information:

$dsn = array(
    'phptype'  => false,
    'dbsyntax' => false,
    'username' => false,
    'password' => false,
    'protocol' => false,
    'hostspec' => false,
    'port'     => false,
    'socket'   => false,
    'database' => false,
    'new_link' => false,
);

Any elements you set override the defaults and the remainder stay at their defaults.

The second parameter is the optional $options array that can contain runtime configuration settings for this package.

Таблица 35-2. List of options

Name	Type	Description
`ssl`	boolean	determines if ssl should be used for connections
`field_case`	integer	CASE_LOWER\|CASE_UPPER: determines what case to force on field/table names
`disable_query`	boolean	determines if queries should be executed
`result_class`	string	class used for result sets
`buffered_result_class`	string	class used for buffered result sets, default is MDB2_Result_Common
`result_wrap_class`	string	class used to wrap result sets into, default is MDB2_Result_Common
`result_buffering`	boolean	should results be buffered or not?
`fetch_class`	string	class to use when fetch mode object is used
`persistent`	boolean	persistent connection?
`debug`	integer	numeric debug level
`debug_handler`	string	function/method that captures debug messages
`debug_expanded_output`	boolean	BC option to determine if more context information should be send to the debug handler
`default_text_field_length`	integer	default text field length to use
`lob_buffer_length`	integer	LOB buffer length
`log_line_break`	string	line-break format
`idxname_format`	string	pattern with '%s' for index name
`seqname_format`	string	pattern with '%s' for sequence name
`savepoint_format`	string	pattern with '%s' for auto generated savepoint names
`seqcol_name`	string	sequence column name
`quote_identifier`	boolean	if identifier quoting should be done when check_option is used
`use_transactions`	boolean	if transaction use should be enabled
`decimal_places`	integer	number of decimal places to handle
`portability`	integer	portability constant
`modules`	array	short to long module name mapping for __call()
`emulate_prepared`	boolean	force prepared statements to be emulated
`datatype_map`	array	map user defined datatypes to other primitive datatypes
`'datatype_map_callback`	array	callback function/method that should be called

In case of success you get a new instance of the database class. It is strongly recommened to check this return value with PEAR::isError() (will detect PEAR_Error or any subclass) or the MDB2_Driver_Common specific isError().

To disconnect use the method disconnect() from your database class instance.

Пример 35-1. Connect and disconnect


<?php
require_once 'MDB2.php';

$dsn = 'pgsql://someuser:apasswd@localhost/thedb';
$options = array(
    'debug' => 2,
    'result_buffering' => false,
);

$mdb2 =& MDB2::factory($dsn, $options);
if (PEAR::isError($mdb2)) {
    die($mdb2->getMessage());
}

// ...

$mdb2->disconnect();
?>

Пример 35-2. Connect using an array for the DSN information


<?php
require_once 'MDB2.php';

$dsn = array(
    'phptype'  => 'pgsql',
    'username' => 'someuser',
    'password' => 'apasswd',
    'hostspec' => 'localhost',
    'database' => 'thedb',
);

$options = array(
    'debug'       => 2,
    'portability' => MDB2_PORTABILITY_ALL,
);

// uses MDB2::factory() to create the instance
// and also attempts to connect to the host
$mdb2 =& MDB2::connect($dsn, $options);
if (PEAR::isError($mdb2)) {
    die($mdb2->getMessage());
}
?>

When connecting to SQLite using a DSN array, the value of the mode element must be a string:


<?php
$dsn = array(
    'phptype'  => 'sqlite',
    'database' => 'thedb',
    'mode'     => '0644',
);
?>

Пример 35-3. Connect to MySQLi via SSL using an array for the DSN information

The ssl element of the $options array must be set to TRUE in order for SSL to work. Each of the extra elements in the $dsn array (key through cipher in the example below) are optional.


<?php
require_once 'MDB2.php';

$dsn = array(
    'phptype'  => 'mysqli',
    'username' => 'someuser',
    'password' => 'apasswd',
    'hostspec' => 'localhost',
    'database' => 'thedb',
    'key'      => 'client-key.pem',
    'cert'     => 'client-cert.pem',
    'ca'       => 'cacert.pem',
    'capath'   => '/path/to/ca/dir',
    'cipher'   => 'AES',
);

$options = array(
    'ssl' => true,
);

// gets an existing instance with the same DSN
// otherwise create a new instance using MDB2::factory()
$mdb2 =& MDB2::singleton($dsn, $options);
if (PEAR::isError($mdb2)) {
    die($mdb2->getMessage());
}
?>

Пример 35-4. Connect to a PostgreSQL database via a socket


<?php
require_once 'MDB2.php';

$dsn = 'pgsql://someuser:apasswd@unix(/tmp)/thedb';
$options = array(
    'debug'       => 2,
    'portability' => MDB2_PORTABILITY_ALL,
);

$mdb2 =& MDB2::factory($dsn, $options);
if (PEAR::isError($mdb2)) {
    die($mdb2->getMessage());
}
?>

Пример 35-5. Connect using singleton


<?php
require_once 'MDB2.php';

$dsn = 'pgsql://someuser:apasswd@localhost/thedb';

$mdb2 =& MDB2::singleton($dsn);
if (PEAR::isError($mdb2)) {
    die($mdb2->getMessage());
}

$blah =& new blah();
// is able to use the existing database connection
$blah->foo();

$mdb2->disconnect();

class blah
{
    function foo() {
        // get a reference to the existing database object
        $mdb2 =& MDB2::singleton();
        // ...
    }
}
?>

См. также

"Intro - Portability", options, setOption(), getOption().

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User Notes:
Note by: uwe.hausdorff@interone.de 2008-08-12 08:31 UTC I had to change some pear sources manually as the oracle parameters NLS_NUMERIC_CHARATERS and NLS_DATE_FORMAT are not editable by the configuration parameters. The setting NLS_DATE_FORMAT is disabled by default, NLS_NUMERIC_CHARATERS are always set. This setting is not european standard and may override individual application settings! see /MDB2/oci8.php in class MDB2_Driver_oci8, function _doConnect on line 395. My file is version "oci8.php,v 1.192 2007/03/04 22:27:11 quipo Exp" if (empty($this->dsn['disable_iso_date'])) { $query = "ALTER SESSION SET NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS'"; $err =& $this->_doQuery($query, true, $connection); if (PEAR::isError($err)) { $this->disconnect(false); return $err; } } $query = "ALTER SESSION SET NLS_NUMERIC_CHARACTERS='. '"; $err =& $this->_doQuery($query, true, $connection); if (PEAR::isError($err)) { $this->disconnect(false); return $err; } Note by: CJ 2008-03-11 13:30 UTC A helpful note that took me days to figure out: When connecting to a MSSQL database, specify the hostname as: "my.host.name,PORT". Don't use a colon, use a comma. That took so long! Note by: user@example.com 2007-11-21 16:14 UTC In PHP5 all objects are passed by reference similar to the way Java does it. From: http://www.php.net/manual/en/language.oop5.basic.php "When assigning an already created instance of a class to a new variable, the new variable will access the same instance as the object that was assigned. This behaviour is the same when passing instances to a function. A copy of an already created object can be made by cloning it." Note by: purej 2007-08-31 19:50 UTC Is this really true here ? Quote: "new return reference automatically" When i read it correctly its just for explicit usage of "new" but thats not the case, we use the Factory methods to get our MDB2 Object. Note by: user@example.com 2007-08-27 18:00 UTC Note that using =& to assign objects is deprecated in PHP5: "Since PHP 5, new return reference automatically so using =& in this context is deprecated and produces E_STRICT level message."