How to Replace MySQL Functions with PDO: A Guide to Modern Database Connectivity in PHP?

How to Replace MySQL Functions with PDO

Introduction:

The MySQL extension is deprecated in PHP and should be replaced with either MySQLi or PDO_MySQL for database connectivity. PDO (PHP Data Objects) offers a modern, object-oriented interface for accessing multiple databases.

Connecting to MySQL and MSSQL Databases:

MySQL:

$dsn = 'mysql:dbname=database_name;host=localhost';
$user = 'username';
$password = 'password';

$dbh = new PDO($dsn, $user, $password);

MSSQL:

$dsn = 'sqlsrv:Server=localhost;Database=database_name';
$user = 'username';
$password = 'password';

$dbh = new PDO($dsn, $user, $password);

Performing Queries:

PDO uses prepared statements for query execution, protecting against SQL injection.

Example SQL:

$SQL = 'SELECT ID, EMAIL FROM users WHERE user = :username';

Executing a Query:

// Prepare statement with array of named variables
$result = $dbh->prepare($SQL);
$result->execute([':username' => $username]);

// OR

// Prepare statement with named placeholder indicator
$result = $dbh->prepare($SQL);
$result->bindValue(':username', $username);
$result->execute();

Fetching Results:

// Fetch a single row as an array
$row = $result->fetch();

// Fetch all rows as an array
$rows = $result->fetchAll();

Using a Helper Class:

To simplify database interactions, consider using a class like the following:

class PDOConnection {
    public $connection;

    public function __construct($dsn, $username, $password) {
        $this->connection = new PDO($dsn, $username, $password);
        $this->connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    }

    public function query($SQL) {
        return $this->connection->query($SQL);
    }

    public function prepare($SQL, $params = []) {
        $result = $this->connection->prepare($SQL);
        $result->execute($params);
        return $result;
    }
}

Example Usage:

$db = new PDOConnection($dsn, $user, $password);

$SQL = 'SELECT ID, EMAIL FROM users WHERE user = :username';
$result = $db->prepare($SQL, ['username' => $username]);

while ($row = $result->fetch()) {
    echo $row['ID'] . ' ' . $row['EMAIL'];
}

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