am using jpgraph to create some bar graphs in php+mysql

Based on some selections, i need to load different pages that displays different graphs based on the selection.have done that using header. am getting all the passed values in the next page. but the graph is not displayed. the browser shows an error like it cant be shown since it contains errors. when i don't use these selections and simply load only a particular graph (using form action) its working fine... i think the problem has something to do with the header function.. please help..