PHP provides two major ways to connect to a MySQL database:

1. MySQLi (MySQL Improved Extension)
2. PDO (PHP Data Objects)

Both methods allow you to run SQL queries, fetch records, insert/update data, and manage the database.
MySQLi is simpler and supports only MySQL, whereas PDO supports 12 different databases like MySQL, PostgreSQL, SQLite, Oracle, etc.

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Connecting Using MySQLi (Procedural Style)

Example

<?php
$servername = "localhost";
$username   = "root";
$password   = "";
$database   = "test_db";

$conn = mysqli_connect($servername, $username, $password, $database);

if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

echo "Connected successfully!";
?>

Steps Explained:

• mysqli_connect() → Creates a connection
• localhost → Server location
• root → Default MySQL username
• test_db → Name of the database you want to connect to
• Program will stop if connection fails (using die())

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Connecting Using MySQLi (Object-Oriented Style)

<?php
$conn = new mysqli("localhost", "root", "", "test_db");

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

echo "Connected successfully!";
?>

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Connecting Using PDO (Recommended)

PDO is flexible, secure, and supports prepared statements.

Example

<?php
$dsn = "mysql:host=localhost;dbname=test_db";
$username = "root";
$password = "";

try {
    $pdo = new PDO($dsn, $username, $password);

    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    echo "Connected successfully!";
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>

Why PDO is better?

• Database-independent
• Improved security
• Easy switching to another database
• Better error handling
• Supports advanced features like prepared statements

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Testing the Connection

After connecting, you can run a sample query to verify:

$sql = "SELECT * FROM users";

$result = mysqli_query($conn, $sql);

if ($result) {
    echo "Query executed!";
}

or with PDO:

$stmt = $pdo->query("SELECT * FROM users");
foreach ($stmt as $row) {
    print_r($row);
}

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Important Notes

Use correct credentials

• Host → usually localhost
• Username → root (XAMPP/WAMP default)
• Password → empty for local servers
• Database name → must exist

Enable MySQL extension

Make sure extensions are enabled in PHP:

• extension=mysqli
• extension=pdo_mysql

Use prepared statements

To prevent SQL Injection.

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Common Errors and Fixes

Error: Access denied

Wrong username/password.

Error: Unknown database

Database does not exist or name is incorrect.

Error: Can’t connect to MySQL server

MySQL service may not be running.

Error: Call to undefined function mysqli_connect()

MySQLi extension disabled → enable in php.ini.

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Example Folder Structure

project/
 ├── connect.php
 ├── index.php
 └── config/
      └── db.php

Always keep database credentials in a separate config file for security.

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Citations

🔗 View other articles about PHP:
http://savanka.com/category/learn/php/

🔗 External PHP Documentation:
https://www.php.net/manual/en/