What are the common pitfalls when trying to insert code into a URL using PHP?

When trying to insert code into a URL using PHP, a common pitfall is not properly encoding the inserted code to prevent it from being interpreted as part of the URL structure. This can lead to errors or security vulnerabilities in your application. To solve this issue, always use functions like `urlencode()` or `rawurlencode()` to encode the inserted code before appending it to the URL.

// Example of properly encoding inserted code in a URL
$code = "your_code_here";
$encoded_code = urlencode($code);
$url = "http://example.com/page.php?code=" . $encoded_code;
echo $url;