What are the potential security risks of using external streams on a PHP server for a custom player?

Potential security risks of using external streams on a PHP server for a custom player include exposing the server to malicious code injection, unauthorized access to sensitive files, and potential denial of service attacks. To mitigate these risks, it is important to validate and sanitize all input from external streams before processing them in the PHP server.

// Example of validating and sanitizing input from an external stream
$stream_url = $_GET['stream_url'];

// Validate the stream URL
if (filter_var($stream_url, FILTER_VALIDATE_URL)) {
    // Sanitize the stream URL
    $sanitized_url = filter_var($stream_url, FILTER_SANITIZE_URL);

    // Process the sanitized stream URL
    // Your code here
} else {
    // Invalid stream URL
    die("Invalid stream URL");
}