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can we have php line graphs , that means dynamically i will get two values (0.0 to 300) then the line graph should indicate the two numbers and also according to numbers changing dynamically the line graph also must change . if this is possible plz help me out
Something like this you mean?
http://www.plus2net.com/php_tutorial/gd-linegp.php
Be warned-- the GD library is very resource intensive and will be at the least slow-- at worst, it'll cause problems with your server (overloading it and possibly getting shut down by the host-- I've had this happen).
However, if you keep your images reasonably small (I wouldn't go much above 300x300px often), then it should be ok.
The documentation and use of the GD library is confusing as well. So if you're going to design your own graphs with it allow yourself lots of time to work through the bugs. With enough patience, it'll eventually result in something usable.
That said, it's a very promising tool you may want to explore.
There is also the option of imagemagick, another library similar to GD that allows image manipulation in PHP. Some like it better, though I'm sure it has its problems too.
For just this purpose (line graphs), the link above looks like a great tool, so don't think I'm saying not to use that-- just that you should know a bit more about GD before getting much beyond that.
IMO, i've never had trouble understanding docs for the GD, it's always been very intuitive for me. As for the slowing the server down problem, it is true that that happens. Be careful with how much stuff you put on it [lines, imagecopy, etc].
It took me a little to get used to some of the basics, but that's easy enough now. I've done some very (maybe too) complicated projects with it and ended up stuck. I wrote a script that did the bluescreen effect from movies (film an actor in front of blue and then the computer removes the blue and puts in a background), and that turned out ok, but still was kinda odd sometimes. And I tried to make a full image editor, which didn't get very far.
But, yes, keep it simple and it'll probably go just fine. Once you get carried away with complexities in GD, though, be prepared for odd results.
The other problem I have with it is that the php.net function references for GD are limited, I feel, compared to what they have for all the other functions. They're useful, just a bit harder to understand (maybe just because there's less attention paid to them because fewer people use the library).