How can the error message "There was an error opening this document. This file is already open or in use by another application" be resolved when working with PDF files in PHP?

When working with PDF files in PHP, the error message "There was an error opening this document. This file is already open or in use by another application" can be resolved by ensuring that the file is properly closed after its use. This error typically occurs when a file is not closed after being opened, causing it to be locked by the application. To fix this issue, make sure to close the file using fclose() function after reading or writing operations are completed.

$file = 'example.pdf';

$handle = fopen($file, 'r');

// Read or write operations on the file

fclose($handle);