Below is the db connection class I came out with so far, but I am going to improve it by extending the PDO class itself,
<?php
class database
{
protected $connection = null;
#make a connection
public function __construct($hostname,$dbname,$username,$password)
{
try
{
# MySQL with PDO_MYSQL
$this->connection = new PDO("mysql:host=$hostname;dbname=$dbname", $username, $password);
$this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch (PDOException $e)
{
$this->connection = null;
die($e->getMessage());
}
}
#get the number of rows in a result
public function num_rows($query)
{
# create a prepared statement
$stmt = $this->connection->prepare($query);
if($stmt)
{
# execute query
$stmt->execute();
return $stmt->rowCount();
}
else
{
return self::get_error();
}
}
#display error
public function get_error()
{
$this->connection->errorInfo();
}
# closes the database connection when object is destroyed.
public function __destruct()
{
$this->connection = null;
}
}
?>
extended class,
class database extends PDO
{
#make a connection
public function __construct($hostname,$dbname,$username,$password)
{
parent::__construct($hostname,$dbname,$username,$password);
try
{
$this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch (PDOException $e)
{
die($e->getMessage());
}
}
#get the number of rows in a result
public function num_rows($query)
{
# create a prepared statement
$stmt = parent::prepare($query);
if($stmt)
{
# execute query
$stmt->execute();
return $stmt->rowCount();
}
else
{
return self::get_error();
}
}
#display error
public function get_error()
{
$this->connection->errorInfo();
}
# closes the database connection when object is destroyed.
public function __destruct()
{
$this->connection = null;
}
}
This is how I instantiate the class,
# the host used to access DB
define('DB_HOST', 'localhost');
# the username used to access DB
define('DB_USER', 'root');
# the password for the username
define('DB_PASS', 'xxx');
# the name of your databse
define('DB_NAME', 'db_2011');
include 'class_database.php';
$connection = new database(DB_HOST,DB_NAME,DB_USER,DB_PASS);
$sql = "
SELECT *
FROM root_contacts_cfm
ORDER BY cnt_id DESC
";
$connection->num_rows($sql);
But I have errors when I call this extended pdo class,
Warning: PDO::__construct() expects parameter 4 to be array, string given in C:\wamp\www\xx\class_database.php on line xx
Fatal error: Call to a member function setAttribute() on a non-object in C:\wamp\www\xx\class_database.php on line xx
I have done some research online, I found this basic structure of extending pdo but I dont understand it...
class myPDO extends PDO
{
public function __construct($dsn,
$username=null,
$password=null,
$driver_options=null)
{
parent::__construct($dsn, $username, $password, $driver_options);
}
public function query($query)
{
$result = parent::query($query);
// do other stuff you want to do here, then...
return($result);
}
}
What is $ds
n variable for? How can I pass my $hostname
variable into extended pdo class?
Another questions: How can I make a method for displaying error in the extended pdo class? How can I close the connection in the extended pdo class?
It is so difficult to move from mysqli to pdo!
Thanks.
$dsn is data source name. It handles your hostname for you. You use it like this:
$dsn = 'mysql:dbname=YOUR_DB_NAME;host=YOUR_HOSTNAME'
With the line $this->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
You have set exceptions to be raised when errors occur (which I like), so in your extended class you can handle errors in exception handlers. If you had a method called getAssoc in your extended PDO class then it would look like this:
/// Get an associative array of results for the sql.
public function getAssoc($sql, $params=array())
{
try
{
$stmt = $this->prepare($sql);
$params = is_array($params) ? $params : array($params);
$stmt->execute($params);
return $stmt->fetchAll(PDO::FETCH_ASSOC);
}
catch (Exception $e)
{
// Echo the error or Re-throw it to catch it higher up where you have more
// information on where it occurred in your program.
// e.g echo 'Error: ' . $e->getMessage();
throw new Exception(
__METHOD__ . 'Exception Raised for sql: ' . var_export($sql, true) .
' Params: ' . var_export($params, true) .
' Error_Info: ' . var_export($this->errorInfo(), true),
0,
$e);
}
}