How to secure PHP include and require statements?

@aniya.jaskolski 

Securing PHP include and require statements is important to prevent potential security vulnerabilities such as remote code inclusion or arbitrary file inclusion attacks. Here are some best practices to help you secure these statements:

1. Validate user input: Always validate and sanitize any user-supplied input before using it in include or require statements. This helps prevent directory traversal attacks where an attacker can manipulate the file path to include sensitive files.
2. Use absolute paths: Instead of relying on relative paths, use absolute paths when including or requiring files. Absolute paths ensure that only the intended files are included and prevent attackers from manipulating the file path.
3. Restrict access: Store your PHP files outside the web root directory or in a directory with restricted access permissions. This prevents direct access to the files, making it harder for attackers to include them maliciously.
4. Disable URL includes: In the PHP configuration (php.ini), ensure that the "allow_url_include" directive is set to "Off." This prevents including files from remote URLs, reducing the risk of including malicious code.
5. Whitelist allowed files: Maintain a whitelist of files that can be included or required in your application. This helps limit the scope of potential vulnerabilities by allowing only specified files to be included.
6. Use file extension restrictions: Restrict the file extensions that can be included or required. For example, if your application only includes .php files, specify this restriction in your code to prevent the inclusion of other file types that might introduce vulnerabilities.
7. Limit file permissions: Set appropriate file permissions for your PHP files, allowing only the necessary read and execute permissions. Restrict write permissions to prevent unauthorized modifications to the included files.
8. Regularly update PHP: Keep your PHP version up to date to take advantage of the latest security patches and improvements. Newer versions often address known vulnerabilities and enhance security.
9. Use a PHP security scanner: Consider using tools like PHP Security Scanner to automatically detect potential security vulnerabilities in your code, including insecure include and require statements.
10. Apply input filtering: Implement input filtering mechanisms such as input validation and output escaping to prevent cross-site scripting (XSS) and other injection attacks. This helps ensure that the data included or required from external sources is safe to use.

By following these best practices, you can significantly reduce the risk associated with PHP include and require statements and enhance the security of your PHP applications.