What are the potential pitfalls of trying to convert JavaScript code into valid JSON format in PHP?

When converting JavaScript code into valid JSON format in PHP, a potential pitfall is that PHP may not handle certain JavaScript syntax correctly, leading to errors in the JSON output. To solve this issue, use the `json_encode()` function in PHP to convert the JavaScript code into valid JSON format.

$javascript_code = '{ "key": "value" }'; // JavaScript code
$json_output = json_encode(json_decode($javascript_code)); // Convert JavaScript code into valid JSON format
echo $json_output; // Output the valid JSON format