PHP PDO

Setting up a connection to MySQL:

try {
$db = new PDO('mysql:host=localhost;dbname=testdb', $login, $passwd);
} catch (PDOException $e) {
echo $e->getMessage();
}

// закрытия соединения и освобождение ресурсов
$db = NULL;

connection with encoding consideration:

$db = new PDO('mysql:host=xxxx.ua;dbname=xxxx', $this->login, $this->passwd, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));

PDO provides two ways to execute a query:

• preparing variables – recommended for speed && security
• direct execution

Queries that modify data are executed via the exec() method:

$db->exec(“INSERT INTO users (login) VALUES(‘john’)”);
$id = $db->lastInsertId();
$db->exec(“UPDATE user SET login=‘alex’”)

The exec method returns a value – the number of affected rows, or FALSE in case of an error.

Queries that retrieve data are executed via the query() method:

$res = $db->query(“SELECT * FROM users”);

Returns FALSE in case of an error.

Escaping special characters (escaping values): $db->quote($_POST[‘login’])

Possible ways to fetch data:

• array (numeric or associative index)
• string (for a column)
• objects
• callback function
• lazy loading
• lazy loading
• iterators

Fetching an array:

$res = $db->query(“SELECT * FROM users”);
while ($row = $res->fetch(PDO::FETCH_NUM)){
// $row - массив с числовыми ключами
}

$res = $db->query(“SELECT * FROM users”);
while ($row = $res->fetch(PDO::FETCH_ASSOC)){
// $row - ассоциативный массив значений, ключи - названия столбцов
}

$res = $db->query(“SELECT * FROM users”);
while ($row = $res->fetch(PDO::FETCH_BOTH)){
// $row - числовой и ассоиативный массив
}

Fetching a single column:

$column = $db->query(“SELECT id FROM users WHERE login=‘login’ AND password=‘password’”);
$user = $column->fetchColumn())

Fetching an object:

$res = $db->query(“SELECT * FROM users”);
while ($obj = $res->fetch(PDO::FETCH_OBJ)) {
// $obj - экземпляр объекта stdClass, имена столбцов - свойства объекта
}

Fetching as an iterator (Iterator interface)

$res = $db->query(“SELECT * FROM users”, PDO::FETCH_ASSOC);
foreach ($res as $row) {
// $row - ассоциативный массив значений
}

Lazy loading – returns the result as an object, but the actual population of the object with values occurs only upon the first access to that field:

$res = $db->query(“SELECT * FROM users”, PDO::FETCH_LAZY);
foreach ($res as $row) {
echo $row[‘name’]; // получение значения
}

Retrieving all fetched values at once:

$qry = “SELECT * FROM users”;
$res = $db->query($qry)->fetchAll(PDO::FETCH_ASSOC);
// $res - массив всей выборки, каждая строка представлена ассоциативным массивом

Processing the fetch result with a callback function:

function add_salt($login,$passw) { … }
$res = $db->query(“SELECT * FROM users”);
$res->fetchAll(PDO::FETCH_FUNC, “add_salt”);

Capabilities of pre-prepared queries:

• compiled once, executed the required number of times
• clear separation between structure and input data (prevention of SQL injection)
• fast execution compared to query()/exec(), even for single execution

Example query:

$stmt = $db->prepare(“SELECT * FROM users WHERE id=?”);
$stmt->execute(array($_GET[‘id’]));
$stmt->fetch(PDO::FETCH_ASSOC);

Parameters for the query can be given by name and bound to variables:

$db->prepare('SELECT * FROM users WHERE name=:name AND email=:email');
$db->execute(array(':name'=>john,':email'=>'john@domain.com'));
$result = $db->fetchAll();
print_r($result);

$dbh->execute(array(':name'=>'alex',':email'=>'alex@domain.com'));
print_r($result);

// пример использования метода bindParam()
try{
$sql = $db->prepare("INSERT INTO USERS(name,email) VALUES (:name,:email)");
$sql->bindParam(':name',$name);
$sql->bindParam(':email',$email);

// назначение значений и вставка новой строки

$name='Joy';
$email='joy@domain.com';
$dbh->exec();

$name='debian';
$email='debian@domain.com';
$dbh->exec();
}
catch(PDOException $e) {
$dbh->rollBack();
echo 'Error : '.$e->getMessage();
}

Transactions. Almost all PDO drivers can work with transactions:

$db->beginTransaction();
if ($db->exec($qry) === FALSE) {
$db->rollback();
}
$db->commit();

Retrieving meta information about the query – number of columns and information about all columns:

$res = $db->query($qry);
$ncols = $res->columnCount();
for ($i=0; $i < $ncols; $i++) {
$meta_data = $res->getColumnMeta($i);
}

Extending PDO capabilities:

class DB extends PDO
{
function query($qry, $mode=NULL)
{
$res = parent::query($qry, $mode);
if (!$res) {
var_dump($qry, $this->errorInfo());
return null;
} else {
return $res;
}
}
}