What role do file permissions play in the successful execution of PHP scripts for file downloads, and how can they be managed effectively?

File permissions play a crucial role in the successful execution of PHP scripts for file downloads. In order for PHP to read or download a file, the file must have the appropriate permissions set to allow PHP to access it. To manage file permissions effectively, you can use the chmod function in PHP to set the desired permissions on the file.

// Set file permissions to allow PHP to read/download the file
chmod("path/to/file", 0644);