Export/Import Tool JNeuhoff - Call to undefined function is

Hi there
(I just saw this same problem on the extension's comments page but I think it needs to be asked here)
I'm upgrading an old Opencart 1.4 shop and trying to use this great extension. I upgraded the site to 1.5 and used this tool to export products and categories into a new 2.2 install. I've used an excel file exported from the 2.2 version and pasted the contents of the files exported from 1.4 version as they're not compatible.
Anyway - the categories imported fine but I'm getting this error with the products:

Call to undefined function isInteger()

And the error log says:
PHP Fatal Error: Call to undefined function isInteger() in /home/giftsfromwales/public_html/newsite16/admin/model/tool/export_import.php on line 3977

I'm afraid I'm a little lost when it comes to PHP but that line seems to be about the 'product_id':

if (!isInteger($product_id)) {
$msg = str_replace( '%2', $product_id, str_replace( '%1', 'Products', $this->language->get( 'error_invalid_product_id' ) ) );
$this->log->write( $msg );
$ok = false;
continue;
}

Many thanks in advance for any help

I got the same problem, the version is 2.2.0.0

I'm having an issue with the export/import extension - after I install it, I can't find it in the menu of the admin pages. I've uninstalled and reinstalled, verified the FTP is pointing to the directory of where the directory ocart2 is found, but not there. Any suggestions what I might be doing wrong?

Found this post on another thread that seems to have sorted this problem:
There was a bug, please install the latest version 3.1 of the Export/Import tool.

I did solve my issue - I'm a newbie to OpenCart and didn't follow the instructions on adding permissions for the extension. My bad. After all was said and done, this extension wasn't for me in the end.