(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)
PDO::__construct — Creates a PDO instance representing a connection to a database
Creates a PDO instance to represent a connection to the requested database.
The Data Source Name, or DSN, contains the information required to connect to the database.
In general, a DSN consists of the PDO driver name, followed by a colon, followed by the PDO driver-specific connection syntax. Further information is available from the PDO driver-specific documentation.
The dsn parameter supports three different methods of specifying the arguments required to create a database connection:
dsn contains the full DSN.
dsn
consists of uri:
followed by a URI that defines the location of a file containing
the DSN string. The URI can specify a local file or a remote URL.
uri:file:///path/to/dsnfile
dsn
consists of a name
name
that maps to
pdo.dsn.name
in php.ini
defining the DSN string.
Note: The alias must be defined in php.ini, and not .htaccess or httpd.conf
The user name for the DSN string. This parameter is optional for some PDO drivers.
The password for the DSN string. This parameter is optional for some PDO drivers.
A key=>value array of driver-specific connection options.
Returns a PDO object on success.
PDO::__construct() throws a PDOException if the attempt to connect to the requested database fails.
Example #1 Create a PDO instance via driver invocation
<?php
/* Connect to an ODBC database using driver invocation */
$dsn = 'mysql:dbname=testdb;host=127.0.0.1';
$user = 'dbuser';
$password = 'dbpass';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
?>
Example #2 Create a PDO instance via URI invocation
The following example assumes that the file /usr/local/dbconnect exists with file permissions that enable PHP to read the file. The file contains the PDO DSN to connect to a DB2 database through the PDO_ODBC driver:
odbc:DSN=SAMPLE;UID=john;PWD=mypass
The PHP script can then create a database connection by simply passing the uri: parameter and pointing to the file URI:
<?php
/* Connect to an ODBC database using driver invocation */
$dsn = 'uri:file:///usr/local/dbconnect';
$user = '';
$password = '';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
?>
Example #3 Create a PDO instance using an alias
The following example assumes that php.ini contains the following entry to enable a connection to a MySQL database using only the alias mydb:
<?php
/* Connect to an ODBC database using an alias */
$dsn = 'mydb';
$user = '';
$password = '';
try {
$dbh = new PDO($dsn, $user, $password);
} catch (PDOException $e) {
echo 'Connection failed: ' . $e->getMessage();
}
?>