September 03, 2024

PHP Security and Best Practices (Security & Scalability)

PHP has been a widely used language for developing web application for decades now. Which is why it is important to adhere to best programming practices for PHP. Learn about recommended PHP security and PHP practices for scalability.

PHP Best Practices & Security

PHP powers everything from small projects to large-scale CMS platforms like WordPress and frameworks like Laravel. It is essential to write clean, reusable, secure and maintainable PHP code to protect your web application and user data. In this post we will discuss PHP best practices that every developer should follow in order to develop robust and scalable applications.

 

PHP Security & Best Practices for Scalable PHP Applications

Like in many other programming languages, PHP best practices are guidelines for writing clean, secure, and maintainable code. They help developers maximize PHP security, prevent vulnerabilities, improve performance, and build scalable applications. Let's discuss some recommended practices that are essential as a standard and reducing the PHP vulnerabilities in any web application.

 

1: Use Latest PHP Version

With each new PHP version released comes the security fixes and new features, which is why it is one of the simplest ways to improve security by keeping PHP version up-to-date and always stay ahead with critical security updates.

 

2: Follow PSR Coding Standards

The PHP Framework Interop Group (PHP-FIG) publishes PHP Standard Recommendations abbreviated as PSRs. These recommendations define standards for PHP coding style and interfaces that should be followed. Following are the important PSRs to follow:

  1. PSR-1: Standard for basic coding style.
  2. PSR-4: Standard for autoloading.
  3. PSR-12: A guide for extended coding style.
 

3: Write Reusable and Modular Code

Think before developing an application as it grows there might be code that is used in several places. Break down the code into small granular function and classes so it can be reused throughout the application. Following this strategy you will have adapted DRY (Don't Repeat Yourself) approach and have avoided the code duplication.

 

4: Enforce HTTPS Across Web Application

One easy step to secure application is to ensure entire site runs over HTTPS and not just login pages. Use SSL/TLS certificates encrypt data between client and server. Following steps can be taken for this:

  1. Redirect all HTTP requests to HTTPS.
  2. Use Strict-Transport-Security header for additional protection.
 

5: Sanitize and Validate User Input

Form submissions pose a vulnerability risk as attackers may use to submit malicious data. It is a good security practice to always sanitize user input for safety and validate it for correct format.

  1. Use filter_input(), filter_var() and filter_input_array for built-in filters.
  2. Validate URLs, emails, phone numbers before processing and saving to database.

An example of sanitizing and validating is as below:

// Sanitize URL
header('Location: ' . filter_var($_SERVER['HTTP_REFERER'], FILTER_SANITIZE_URL));

// Validate email
$email = filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL);
 

6: Prevent SQL Injection with Prepared Statements

One of the most common vulnerability is SQL injection in which attacker passed malformed data where user input is inserted into SQL query. Which is why it is important to always use prepared SQL query statements which separates the data from query logic and makes it next to impossible for attackers to inject malicious SQL.

$stmt = $pdo->prepare("SELECT * FROM users WHERE email = :email");
$stmt->execute(['email' => $_POST['email']]);
 

7: Protect Against XSS Attacks

One of other vulnerabilities in a web application is Cross-Site-Scripting (XSS) in which attacker injects malicious script code into content that is delivered to user.This happens for example when a web page display some data from query parameter or it is already stored in database. It is important to protect against XSS attack with following steps:

  1. Escape user input before displaying it whether it is coming from database or query parameter.
  2. Add Content-Security-Policy header for additional protection.
// Example from query parameter
echo htmlspecialchars($_GET['comment'], ENT_QUOTES, 'UTF-8');

// Example if malicious code is stored in a variable i.e. coming from database
echo htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');
 

8: Manage Sessions Properly

One of PHP vulnerabilities is session hijacking in which attacker takes over a valid user session by stealing or manipulating session ID. Which makes it important to secure PHP session and manage sessions properly. Steps to reduce the risk of session hijacking are:

  1. Use session_start() at the beginning of scripts.
  2. Use secure and HTTP only cookies.
  3. Regenerate session ID after login.
// Secure session cookies
session_set_cookie_params([
    'secure' => true,        // Only sent over HTTPS
    'httponly' => true,      // Not accessible via JavaScript
    'samesite' => 'Strict',  // Prevent cross-site requests
]);

// Regenerate session ID
session_regenerate_id(true);
 

9: Store Hashed Passwords

One practice that every application follows already is storing hashed passwords. Even the database gets compromised the hashed passwords will be much harder to reverse than plain texts. Always use password_hash() and password_verify() for user passwords.

$hash = password_hash($password, PASSWORD_DEFAULT);

if (password_verify($password, $hash)) {
    // Success
}
 

10: Use Recommended Security Headers

In addition to mentioned practice,s it is considerable to use HTTP security headers to prevent common attacks. Following headers in place can prevent common attacks:

header("Content-Security-Policy: default-src 'self';");
header("X-Frame-Options: DENY");
header("X-Content-Type-Options: nosniff");
header("Referrer-Policy: no-referrer");

We explained some of recommended and best PHP practices to secure a PHP application. By implementing these PHP security practices the risk of common vulnerabilities can be reduced significantly.

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