progress bar for server elaboration php script?

Is there a way to make a progress bar (using ajax and开发者_运维问答 jquery) for any script runnig in the server? I use a php script to elaborate some datas and I want to output a percent info to the client browser of the script progress. I tried to use session var but with poor results.

You can poll your script progress somehow (datas processed are marked with 1 datas that not are marked with 0) you can count the progress percentage.

Note: my tip was an outline only. I don't know how your script crunching your data and the data can or cannot be marked like i said above. What kind of data processing happens in the background?