How to Connect to MySQL in PHP: Simple Guide

To connect to MySQL in PHP, use the mysqli extension by creating a new mysqli object with your database host, username, password, and database name. Check the connection for errors to ensure it is successful.

Syntax

The basic syntax to connect to MySQL in PHP uses the mysqli class. You create a new instance with four parameters: host, username, password, and database name.

• host: The server address, usually localhost.
• username: Your MySQL username.
• password: Your MySQL password.
• database: The name of the database you want to use.

After creating the connection, check if it failed by inspecting the connect_error property.

php

$conn = new mysqli($host, $username, $password, $database);
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

Example

This example shows how to connect to a MySQL database named testdb on localhost with username root and no password. It prints a success message or an error.

php

<?php
$host = "localhost";
$username = "root";
$password = "";
$database = "testdb";

$conn = new mysqli($host, $username, $password, $database);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully to MySQL database.";
?>

Output

Connected successfully to MySQL database.

Common Pitfalls

Common mistakes when connecting to MySQL in PHP include:

• Using wrong credentials (host, username, password, or database name).
• Not checking for connection errors, which can cause silent failures.
• Forgetting to close the connection after use (optional but recommended).
• Using deprecated mysql_connect() instead of mysqli or PDO.

php

<?php
// Wrong way: no error check
$conn = new mysqli("localhost", "root", "", "wrongdb");
// This may cause errors later without notice

// Right way: check connection
$conn = new mysqli("localhost", "root", "", "wrongdb");
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
?>

Quick Reference

Remember these tips when connecting to MySQL in PHP:

• Use mysqli or PDO for modern, secure connections.
• Always check $conn->connect_error after connecting.
• Use localhost as host if your database is on the same server.
• Close the connection with $conn->close(); when done.

Key Takeaways

Use the mysqli class with host, username, password, and database to connect to MySQL in PHP.

Always check for connection errors using the connect_error property.

Avoid deprecated mysql_connect; prefer mysqli or PDO for database connections.

Use localhost as host if your database runs on the same machine as PHP.

Close your database connection after finishing queries to free resources.