How to prevent server-side request forgery attacks in PHP?

@domenico 

1. Validate user input: Input validation is the first step to protect against SSRF attacks. Any user input that is not validated can be manipulated to send requests to an unintended destination.
2. Whitelist allowed URLs: Whitelist the URLs that are allowed to be accessed by the application. This prevents attackers from using other URLs to perform SSRF attacks.
3. Use cURL with CURLOPT_FOLLOWLOCATION set to false: Use cURL for outbound HTTP requests and set CURLOPT_FOLLOWLOCATION to false. This makes sure that the URL being requested is not being redirected.
4. Restrict network access: Restrict network access using a firewall and only allow outgoing requests to trusted IP addresses.
5. Use DNS resolution: Use DNS resolution to check the IP address of the requested URL. This ensures that the requested URL is valid and authorized to be accessed.
6. Limit resource usage: Limit the resources used by outbound HTTP requests. This can prevent attackers from using the application to perform DOS attacks on other websites.
7. Avoid using user-provided input in sensitive operations: Avoid using user-provided input to perform sensitive operations such as database queries and file system operations.
8. Keep software up-to-date: Keep the software and libraries used in the application up-to-date with security patches and updates to reduce the risk of vulnerabilities.