[prog] On the fly graphs with php

[Conor Daly]

On Thu, Jul 14, 2005 at 03:03:43PM -0400 or so it is rumoured hereabouts, 
Clifford Crawford thought:
> On 2005/07/14, at 13:59, Conor Daly wrote:
> 
> >However, if I
> >
> >include("chart.php");
> >
> >I get a "cannot send header" error since other stuff has already  
> >happened.
> 
> My guess is this is what needs to be fixed; you need to be able to  
> set the header to "image/png" so that the browser can correctly  
> interpret the data.  What exactly do you mean by "other stuff has  
> already happened"?  Is it outputting something before showImage() is  
> called?  If it does, then PHP might be setting the header to "text/ 
> html" behind your back.  Also, check for any stray spaces or anything  
> outside of <? ?> tags, that could cause the header to be set wrong too.

Sorry, I'm probably not being clear here.  When running in test mode where
I define the data to plot within chart.php, I can use an 

<img src="chart.php">

to load the image.  At this point, showImage() is sending the correct
header (I don't have the code in front of me now so it's from memory).
However, if I want to pass data to the makeImage() function, I have to
include("foo.php"); before I access that function.  At this point, I
need flags so that it won't attempt to output an image until the
makeImage() function has been called first.  Otherwise, it attempts to put
a 

header("image/png"); 

and fails because the calling script has already put a "text/html" header
while building the page.  So, I'm left in the situation where either I
have to embed up to 1500 datapoints in my call to makeImage() for later
use by an

<img src="chart.php">

tag later in my page.  This isn't working for me yet...

Conor
-- 
Conor Daly <conor.daly at oceanfree.net>

Domestic Sysadmin :-)
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