What are some best practices for testing security vulnerabilities on a self-made PHP forum?

To test security vulnerabilities on a self-made PHP forum, it is important to conduct thorough penetration testing to identify potential weaknesses. This can involve using tools like OWASP ZAP or Burp Suite to scan for common vulnerabilities such as SQL injection, cross-site scripting, and insecure file uploads. Additionally, manual testing should be performed to ensure that user input is properly sanitized and validated to prevent attacks.

// Example code snippet for validating user input in a PHP form
if(isset($_POST['submit'])){
    $username = htmlspecialchars($_POST['username']);
    $password = htmlspecialchars($_POST['password']);
    
    // Validate input to prevent SQL injection
    $username = mysqli_real_escape_string($conn, $username);
    $password = mysqli_real_escape_string($conn, $password);
    
    // Perform further validation and processing here
}