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.
       
 
   Note: 
     These became PHP constants in PHP 4.3.0.