Manuel Pear

Niveau superieur
Sommaire

Connecting

Connecting -- Connecting and disconnecting a database

Description

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

Tableau 39-1. 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,
    'service'  => false, // only in oci8
);
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.

Tableau 39-2. List of options

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

Exemple 39-1. Connect and disconnect

  1. <?php
  2. require_once 'MDB2.php';  
  3.  
  4. $dsn = 'pgsql://someuser:apasswd@localhost/thedb';  
  5. $options = array( 
  6.    'debug' => 2, 
  7.    'result_buffering' => false,  
  8. );  
  9.  
  10. $mdb2 =& MDB2::factory($dsn, $options);  
  11. if (PEAR::isError($mdb2)) { 
  12.    die($mdb2->getMessage());  
  13. }  
  14.  
  15. // ...
  16.  
  17. $mdb2->disconnect();  
  18.  
  19. ?> 

Exemple 39-2. Connect using an array for the DSN information

  1. <?php
  2. require_once 'MDB2.php';  
  3.  
  4. $dsn = array( 
  5.    'phptype' => 'pgsql', 
  6.    'username' => 'someuser', 
  7.    'password' => 'apasswd', 
  8.    'hostspec' => 'localhost', 
  9.    'database' => 'thedb',  
  10. );  
  11.  
  12. $options = array( 
  13.    'debug'   => 2, 
  14.    'portability' => MDB2_PORTABILITY_ALL,  
  15. );  
  16.  
  17. // uses MDB2::factory() to create the instance
  18. // and also attempts to connect to the host
  19. $mdb2 =& MDB2::connect($dsn, $options);  
  20. if (PEAR::isError($mdb2)) { 
  21.    die($mdb2->getMessage());  
  22. }  
  23.  
  24. ?> 

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

  1. <?php
  2. $dsn = array( 
  3.    'phptype' => 'sqlite', 
  4.    'database' => 'thedb', 
  5.    'mode'   => '0644',  
  6. );  
  7.  
  8. ?> 

Exemple 39-3. 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.

  1. <?php
  2. require_once 'MDB2.php';  
  3.  
  4. $dsn = array( 
  5.    'phptype' => 'mysqli', 
  6.    'username' => 'someuser', 
  7.    'password' => 'apasswd', 
  8.    'hostspec' => 'localhost', 
  9.    'database' => 'thedb', 
  10.    'key'   => 'client-key.pem', 
  11.    'cert'   => 'client-cert.pem', 
  12.    'ca'   => 'cacert.pem', 
  13.    'capath' => '/path/to/ca/dir', 
  14.    'cipher' => 'AES',  
  15. );  
  16.  
  17. $options = array( 
  18.    'ssl' => true,  
  19. );  
  20.  
  21. // gets an existing instance with the same DSN
  22. // otherwise create a new instance using MDB2::factory()
  23. $mdb2 =& MDB2::singleton($dsn, $options);  
  24. if (PEAR::isError($mdb2)) { 
  25.    die($mdb2->getMessage());  
  26. }  
  27.  
  28. ?> 

Exemple 39-4. Connect to a PostgreSQL database via a socket

  1. <?php
  2. require_once 'MDB2.php';  
  3.  
  4. $dsn = 'pgsql://someuser:apasswd@unix(/tmp)/thedb';  
  5. $options = array( 
  6.    'debug'   => 2, 
  7.    'portability' => MDB2_PORTABILITY_ALL,  
  8. );  
  9.  
  10. $mdb2 =& MDB2::factory($dsn, $options);  
  11. if (PEAR::isError($mdb2)) { 
  12.    die($mdb2->getMessage());  
  13. }  
  14.  
  15. ?> 

Exemple 39-5. Connect using singleton

  1. <?php
  2. require_once 'MDB2.php';  
  3.  
  4. $dsn = 'pgsql://someuser:apasswd@localhost/thedb';  
  5.  
  6. $mdb2 =& MDB2::singleton($dsn);  
  7. if (PEAR::isError($mdb2)) { 
  8.    die($mdb2->getMessage());  
  9. }  
  10.  
  11. $blah =& new blah();  
  12. // is able to use the existing database connection
  13. $blah->foo();  
  14.  
  15. $mdb2->disconnect();  
  16.  
  17. class blah  
  18. { 
  19.    function foo() { 
  20.       // get a reference to the existing database object
  21.       $mdb2 =& MDB2::singleton(); 
  22.       // ...
  23.    }  
  24. }  
  25.  
  26. ?> 

Voir aussi

<< Intro - Portability >>, options, setOption(), getOption().

Niveau superieur
Sommaire

Remonter Remonter
L'éditeur javascript - CSS - Gentoo - Tutoriaux PHP - Tutoriels PHP - Bretagne - php - Moto - Kit graphique