PHP: Handling Databases and Server-Side Logic

PHP uses MySQLi and PDO extensions to interact in database operations and server-side logic processing, and processes server-side logic through functions such as session management. 1) Use MySQLi or PDO to connect to the database and execute SQL queries. 2) Handle HTTP requests and user status through session management and other functions. 3) Use transactions to ensure the atomicity of database operations. 4) Prevent SQL injection, use exception handling and closing connections for debugging. 5) Optimize performance through indexing and cache, write highly readable code and perform error handling.

introduction

In modern web development, PHP plays a crucial role as a powerful server-side scripting language. Whether you are a beginner or an experienced developer, understanding how to handle database and server-side logic in PHP is a crucial skill. This article will take you to explore the application of PHP in database operations and server-side logic processing, helping you master these key technologies.

By reading this article, you will learn how to use PHP to interact with a database, how to write efficient server-side logic, and how to avoid common pitfalls and errors. Whether you are building a simple blogging system or a complex e-commerce platform, this knowledge will provide you with a solid foundation.

Review of basic knowledge

Before we dive into it, let's review the basics related to PHP database and server-side logic. PHP provides a variety of extensions to interact with databases, such as MySQLi and PDO, which allow you to perform SQL queries, manage database connections, and more. In addition, PHP's server-side logical processing involves handling HTTP requests, session management, error handling, etc.

For example, the MySQLi extension allows you to interact with MySQL databases in an object-oriented way, while PDO (PHP Data Objects) provides a more general database access layer that supports multiple database systems.

Core concept or function analysis

Database operations

In PHP, database operations are implemented through steps such as connecting to the database, executing queries, and processing result sets. Let's look at a simple example using MySQLi extension:

 <?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create a connection $conn = new mysqli($servername, $username, $password, $dbname);

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

// Execute the query $sql = "SELECT id, firstname, lastname FROM MyGuests";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Output data while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"]. "<br>";
    }
} else {
    echo "0 results";
}
$conn->close();
?>

This example shows how to connect to a MySQL database, execute a simple SELECT query, and output the results. It is worth noting that MySQLi provides two ways to use object-oriented and procedural. Here we choose the object-oriented approach because it is more in line with modern programming habits.

Server-side logic processing

Server-side logical processing involves processing HTTP requests, managing sessions, processing form submissions, etc. Let's look at a simple session management example:

 <?php
session_start();

if (!isset($_SESSION["views"])) {
    $_SESSION["views"] = 0;
}
$_SESSION["views"] = $_SESSION["views"] 1;
echo "Page views: " . $_SESSION["views"];
?>

This example shows how to use PHP's session management feature to track user page views. Session management is an important aspect of server-side logic processing, which allows you to maintain state between different requests from users.

Example of usage

Basic usage

Let's look at a more complex example showing how to handle database operations and server-side logic in PHP:

 <?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create a connection $conn = new mysqli($servername, $username, $password, $dbname);

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

// Process form submission if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    $email = $_POST["email"];

    // Execute the insert query $sql = "INSERT INTO users (name, email) VALUES (&#39;$name&#39;, &#39;$email&#39;)";

    if ($conn->query($sql) === TRUE) {
        echo "New record insertion successfully";
    } else {
        echo "Error: " . $sql . "<br>" . $conn->error;
    }
}

$conn->close();
?>

This example shows how to process form submissions and insert data into the database. It should be noted that there is no input verification and SQL injection protection in this example, which is very dangerous in practical applications.

Advanced Usage

In practical applications, you may need to deal with more complex logic and database operations. Let's look at an example using transactions:

 <?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create a connection $conn = new mysqli($servername, $username, $password, $dbname);

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

// Start the transaction $conn->autocommit(FALSE);

try {
    // Execute multiple queries $sql1 = "INSERT INTO users (name, email) VALUES (&#39;John Doe&#39;, &#39;john@example.com&#39;)";
    $sql2 = "INSERT INTO orders (user_id, product_id) VALUES (LAST_INSERT_ID(), 1)";

    if ($conn->query($sql1) === TRUE && $conn->query($sql2) === TRUE) {
        // commit transaction $conn->commit();
        echo "Transaction success";
    } else {
        // Rollback transaction $conn->rollback();
        echo "transaction failed";
    }
} catch (Exception $e) {
    // Rollback transaction $conn->rollback();
    echo "Transaction failed: " . $e->getMessage();
}

$conn->close();
?>

This example shows how to use transactions to ensure the atomicity of multiple database operations. Transactions are a high-level concept in database operations, which allows you to treat multiple operations as a whole, either all succeed or all fail.

Common Errors and Debugging Tips

Common errors when handling database and server-side logic include SQL injection, unhandled exceptions, unclosed database connections, etc. Let's look at some debugging tips:

• SQL injection protection : Use preprocessing statements and parameterized queries to prevent SQL injection. For example:

 <?php
$stmt = $conn->prepare("INSERT INTO users (name, email) VALUES (?, ?)");
$stmt->bind_param("ss", $name, $email);
$stmt->execute();
?>

• Exception handling : Use the try-catch block to catch and handle exceptions. For example:

 <?php
try {
    // Database operation} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
}
?>

• Close connection : Make sure to close the database connection at the end of the script. For example:

 <?php
$conn->close();
?>

Performance optimization and best practices

Performance optimization and best practices are crucial in practical applications. Let's look at some suggestions:

• Using Index : Adding indexes to commonly used query fields in the database can significantly improve query performance. For example:

 <?php
$sql = "CREATE INDEX idx_name ON users(name)";
$conn->query($sql);
?>

• Cache query results : Use the cache mechanism to reduce the number of database queries. For example:

 <?php
if (!isset($cache[&#39;users&#39;])) {
    $result = $conn->query("SELECT * FROM users");
    $cache[&#39;users&#39;] = $result->fetch_all(MYSQLI_ASSOC);
}
?>

• Code readability : Write highly readable code, using meaningful variable names and comments. For example:

 <?php
// Get the user list $users = $conn->query("SELECT * FROM users")->fetch_all(MYSQLI_ASSOC);
?>

• Error handling : Use appropriate error handling mechanisms to avoid exposure of sensitive information. For example:

 <?php
if ($conn->connect_error) {
    http_response_code(500);
    echo "Internal Server Error";
    exit;
}
?>

With these examples and suggestions, you should have a deeper understanding of the processing of database and server-side logic in PHP. Remember that practice is the best way to master these skills, so don’t be afraid to try and make mistakes. I wish you a happy programming!

The above is the detailed content of PHP: Handling Databases and Server-Side Logic. For more information, please follow other related articles on the PHP Chinese website!