If you are unable to move a file using PHP's move_uploaded_file, add the following code to the PHP file which uploads the file.
ini_set('display_errors',1); error_reporting(E_ALL); echo '<pre>'; print_r($_FILES); echo '</pre>';
Following are common errors, and the solutions for the errors.
Warning: move_uploaded_file(uploads/1.png): failed to open stream: Permission denied in D:\path\to\image_upload.php on line 28
Warning: move_uploaded_file(): Unable to move 'D:\php\upload_tmp\phpEE37.tmp' to 'uploads/1.png' in D:\path\to\pbsmart\image_upload.php on line 28