Handling file upload errors

The $_FILES["FILE_NAME"]['error'] (where "FILE_NAME" is the value of the name attribute of the file input, present in your form) might contain one of the following values:

1. UPLOAD_ERR_OK - There is no error, the file uploaded with success.
2. UPLOAD_ERR_INI_SIZE - The uploaded file exceeds the upload_max_filesize directive in php.ini.
3. UPLOAD_ERR_PARTIAL - The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form.
4. UPLOAD_ERR_NO_FILE - No file was uploaded.
5. UPLOAD_ERR_NO_TMP_DIR - Missing a temporary folder. (From PHP 5.0.3).
6. UPLOAD_ERR_CANT_WRITE - Failed to write file to disk. (From PHP 5.1.0).
7. UPLOAD_ERR_EXTENSION - A PHP extension stopped the file upload. (From PHP 5.2.0).

An basic way to check for the errors, is as follows:

<?php
$fileError = $_FILES["FILE_NAME"]["error"]; // where FILE_NAME is the name attribute of the file input in your form
switch($fileError) {
    case UPLOAD_ERR_INI_SIZE:
        // Exceeds max size in php.ini
        break;
    case UPLOAD_ERR_PARTIAL:
        // Exceeds max size in html form
        break;
    case UPLOAD_ERR_NO_FILE:
        // No file was uploaded
        break;
    case UPLOAD_ERR_NO_TMP_DIR:
        // No /tmp dir to write to
        break;
    case UPLOAD_ERR_CANT_WRITE:
        // Error writing to disk
        break;
    default:
        // No error was faced! Phew!
        break;
}