Since PHP 4.2.0, PHP returns an appropriate error code along with the
file array. The error code can be found in the
error segment of the file array that is created
during the file upload by PHP. In other words, the error might be
found in $_FILES['userfile']['error'].
UPLOAD_ERR_OK
Value: 0; There is no error, the file uploaded with success.
UPLOAD_ERR_INI_SIZE
Value: 1; The uploaded file exceeds the
upload_max_filesize
directive in php.ini.
UPLOAD_ERR_FORM_SIZE
Value: 2; The uploaded file exceeds the MAX_FILE_SIZE
directive that was specified in the HTML form.
UPLOAD_ERR_PARTIAL
Value: 3; The uploaded file was only partially uploaded.
UPLOAD_ERR_NO_FILE
Value: 4; No file was uploaded.
UPLOAD_ERR_NO_TMP_DIR
Value: 6; Missing a temporary folder. Introduced in PHP 4.3.10 and PHP
5.0.3.
UPLOAD_ERR_CANT_WRITE
Value: 7; Failed to write file to disk. Introduced in PHP 5.1.0.
UPLOAD_ERR_EXTENSION
Value: 8; File upload stopped by extension. Introduced in PHP 5.2.0.