exec won't pass arg with spaces

I'm trying to execute /usr/bin/convert passing the image size and the file name, the problem is that the file name contains lots of spaces, so I try to pass "filename with lots of spaces", and nothing works. I've read something about safe mode, but I have safe mode disabled; I also read something about a bug, but nothing definitive. Can someone point me in the right direction? Here's is my configuration: Red Hat Linux 9 php-4.2.2-17.2 httpd-2.0.40-21.3 Sample code:

        exec("$imagemagickPath/convert -geometry " .
        "{$thumbnail_width}x{$thumbnail_height} " .
        "$images_dir/$filename $images_dir/tb_$filename");

where filename could be: /var/www/html/images/SPIN CoreRT1 to EX-JF1 (cw - kpi - KPI Performance Report(Weekly).png What I'm trying to do is simply create thumbnails of images stored in a directory, there are thounsands of images. I've tried to send the complete strings to a externa script that executes convert, but at the moment of exectution the " are removed and the scripts fails. Here is a extract of the /var/log/httpd/error_log convert: Unable to open file (/var/www/html/ivexport/spinkpi_offline/tb_SPIN - Core-Rt2 POS to ATL (cw - WAN Link Performance - 3 Daily).png). I'm not very experienced with PHP, and it's been a coulpe of years since I coded. Any help would be greatly appreciated. Regards, Raúl Millán