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();
// ...
}
}
?> |
|