The ultimate guide to PHP database connections: covers everything you need to know

PHP database connection involves database host name, database name, connection establishment (mysqli_connect()), error handling (mysqli_error() and mysqli_errno()), persistent connection (mysqli_pconnect()), and advanced features such as prepared statements, Transactions and practical cases (reading user data).

The Ultimate Guide to PHP Database Connections

Preface

Interacting with the database is The key to building dynamic web applications. PHP provides various options for establishing strong and reliable database connections. This article will provide a comprehensive introduction to PHP database connection technology, from basic concepts to advanced techniques.

Database connection basics

A database connection consists of two main elements:

1. Database host name or IP address: The network address of the database server.
2. Database Name: The name of the specific database to connect to.

Establishing a connection

To establish a connection with the database, you can use PHP's mysqli_connect() function:

$mysqli = mysqli_connect("localhost", "root", "password", "database_name");

This function returns a mysqli object, which represents the connection to the database. If the connection fails, it returns false.

Error handling

Error handling is critical to ensuring the reliability of the code that connects to the database. Use mysqli functions mysqli_error() and mysqli_errno() to get connection error information:

if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;
}

persistent connection

persistent Connections help improve application performance because they reuse previously established connections. To enable persistent connections, use mysqli_pconnect() Function:

$mysqli = mysqli_pconnect("localhost", "root", "password", "database_name");

Advanced Features

Prepared Statements

Prepared statements can prevent SQL injection attacks and improve query performance:

$stmt = $mysqli->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);
$stmt->execute();

Transactions

Transactions allow you to combine multiple database operations into a single transaction sexual unit. If any operation fails, the entire transaction will be rolled back:

$mysqli->begin_transaction();
$mysqli->query("INSERT INTO orders (product_id, quantity) VALUES (1, 5)");
$mysqli->commit();

Practical case: Reading user data

Assume you have a users table, It contains id, username, email columns. Create a PHP script to read all user information:

$mysqli = mysqli_connect("localhost", "root", "password", "database_name");

if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: (" . $mysqli->connect_errno . ") " . $mysqli->connect_error;
}

$sql = "SELECT * FROM users";
$result = $mysqli->query($sql);

if ($result->num_rows > 0) {
  while ($row = $result->fetch_assoc()) {
    echo "ID: " . $row["id"] . "
";
    echo "Username: " . $row["username"] . "
";
    echo "Email: " . $row["email"] . "

";
  }
} else {
  echo "No users found.";
}

$mysqli->close();

Conclusion

By following the steps described in this article, you can establish a strong and reliable PHP database connection. Improve the performance and security of your code with prepared statements, transactions, and advanced features.

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