Magento offers some nice charts and reports. Today we noticed an issue on client's back-end Magento dashboard, the turnover and order charts were not generated properly.
The answer to this problem is very simple. If your server is behind a properly configured firewall it will probably block any request to unknown URLs. For example to URLs like: http://chart.apis.google.com/chart
In order to solve this problem you can consider to implement either of the 2 solutions below.
Solution 1: Allow access to this URL on your firewall:
Solution 2: Make sure Magento does not try to fetch the image through PHP
Locate this file: app/design/adminhtml/default/default/template/dashboard/graph.phtml
And change: "getChartUrl()" to "getChartUrl(true)"
This will cause Magento to just return the image location at http://chart.apis.google.com/chart instead of downloading it through PHP.
Both solutions seem to work great. But Solution 2 could throw a warning if you are running your Magento back-end on an SSL connection (which should be doing by the way!)
After implementing this solution the Magento charts or graphs are shown and you can again admire your sales figures!