How can file permissions affect file upload functionality in PHP?

File permissions can affect file upload functionality in PHP if the directory where files are uploaded does not have the correct permissions set. If the directory does not have the appropriate write permissions, PHP will not be able to upload files to that directory. To solve this issue, you need to ensure that the directory where files are uploaded has the correct permissions set to allow PHP to write to it.

// Set the correct permissions for the upload directory
chmod("uploads/", 0777);