What are the potential issues with using FTP to upload files in a PHP application, especially when it comes to file permissions and server configurations?

Potential issues with using FTP to upload files in a PHP application include security vulnerabilities, file permission errors, and server configuration limitations. To address these issues, it is important to ensure that proper file permissions are set for uploaded files and directories, and to validate user input to prevent malicious file uploads.

// Example code snippet to address file permission issues when uploading files via FTP in PHP

// Set file permissions for uploaded files and directories
ftp_chmod($ftp_conn, 0644, $remote_file); // Set file permissions to 0644
ftp_chmod($ftp_conn, 0755, $remote_dir); // Set directory permissions to 0755