When uploading files in PHP, there are several errors that can occur. According to the official PHP documentation, the following are the most common types of errors that can occur during file uploads,
Error Code Description
0 There is no error, the file uploaded with success.
1 The uploaded file exceeds the upload_max_filesize directive in php.ini.
2 The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.
3 The uploaded file was only partially uploaded.
4 No file was uploaded.
6 Missing a temporary folder.
7 Failed to write file to disk.
8 A PHP extension stopped the file upload.
You can access the error code associated with a file upload in PHP using the $_FILES['userfile']['error'] array.