What are common reasons for receiving a "Permission denied" error when trying to upload a file using PHP?

When receiving a "Permission denied" error when trying to upload a file using PHP, it typically means that the directory where you are trying to upload the file does not have the necessary write permissions. To solve this issue, you need to ensure that the directory has the correct permissions set to allow PHP to write files to it.

// Ensure the directory where you are uploading the file has the correct permissions set
// For example, set the directory permissions to 755
chmod('/path/to/upload/directory', 0755);