What potential issues could arise when trying to upload files using PHP?

One potential issue when trying to upload files using PHP is the default file size limit set in the PHP configuration. This can prevent users from uploading larger files. To solve this issue, you can increase the `upload_max_filesize` and `post_max_size` directives in the php.ini file.

// Increase file upload size limit
ini_set('upload_max_filesize', '20M');
ini_set('post_max_size', '25M');