What are the potential reasons for encountering empty output or errors when uploading and processing files in PHP?

One potential reason for encountering empty output or errors when uploading and processing files in PHP is incorrect file permissions. Ensure that the directory where the files are being uploaded has the correct permissions set to allow PHP to write to it. Additionally, check for any errors in the PHP code related to file handling functions or file processing logic.

// Check file permissions
// Ensure that the directory where files are uploaded has correct permissions (e.g., 755)
// Make sure PHP has write permissions to the upload directory

// Example code to set correct permissions
chmod("/path/to/upload/directory", 0755);