This software has weird configuration options to enable the display of errors. To be able to see errors, you should set the following in
$PHPTHUMB_CONFIG['error_die_on_error'] = true; // die with error message on any fatal error (recommended with standalone phpThumb.php) $PHPTHUMB_CONFIG['error_silent_die_on_error'] = false; // simply die with no output of any kind on fatal errors (not recommended) $PHPTHUMB_CONFIG['error_die_on_source_failure'] = true; // die with error message if source image cannot be processed by phpThumb() (usually because source image is corrupt in some way). If false the source image will be passed through unprocessed, if true (default) an error message will be displayed.
But also, and this is the tricky one as it’s away from the other error parameters, you need to enable (or rather, “not disable”) debug mode:
$PHPTHUMB_CONFIG['disable_debug'] = false;
Now phpThumb’s output will still seem like an image to your browser, but if you save it and open it with notepad or equivalent, you’ll be able the read the error message.