[Sommaire] [Imprimer]

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  28  <H2><A NAME="5_2">5.2 Using the cache in your script</A></H2>
  29  <P> To use caching in your script you must supply a suitable file name
  30   which will be used to store the image in the cache. You can also supply
  31   a timeout value indicating how many minutes the cached image should be
  32   considered valid.</P>
  33  <P> These parameters are supplied in the initial Graph() method call
  34   which should be among the first in your script. Instead of manually
  35   specifying a file name to be used you could often use the special name
  36   &quot;auto&quot;. If the filename is specified as &quot;auto&quot; the cashed image will
  37   then be named the same as the image script but with the correct
  38   extension depending on what image format have been chosen.</P>
  39  <P> If you don't specify a file name no caching will be used no matter
  40   the settings of USE_CACHE (without a file name it is impossible!)</P>
  41  <P> The following call to Graph() shows a typical use of the cache.</P>
  42  <P><DIV class="phpscript"><CODE><FONT color="#000000"> <FONT color="#0000BB">
  43  &nbsp;$graph&nbsp;</FONT><FONT color="#007700">=&nbsp;new&nbsp;</FONT><FONT color="#0000BB">
  44  Graph</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">300</FONT><FONT
  45  color="#007700">,</FONT><FONT color="#0000BB">200</FONT><FONT color="#007700">
  46  ,</FONT><FONT color="#DD0000">&quot;auto&quot;</FONT><FONT color="#007700">,</FONT><FONT
  47  color="#0000BB">60</FONT><FONT color="#007700">)</FONT><FONT color="#0000BB">
  48  </FONT></FONT></CODE></DIV></P>
  49  <P></P>
  50  <P> The above code will use the automatic filename and a make the cache
  51   valid for 60 minutes.</P>
  52  <P> So, how does this all work now?</P>
  53  <P> The first time you call your script (no cached image) everything
  54   will be as usual, the script will run and you will in the end send back
  55   the image to the browser. However if you have the caching enabled
  56   JpGraph will automatically have stored a copy of the generated image in
  57   the cache directory.</P>
  58  <P> The next time you call the script the first thing that happens in
  59   the initial Graph() is that it will go and check in the cache directory
  60   if the named image exists there. If this is the case it will also
  61   checks that the image isn't too old (as compared to the specified
  62   timeout value). If the image is valid then the image will be streamed
  63   straight back from the image file to the browser and the script will
  64   end it's execution.</P>
  65  <P> Hence, if the image is found in the cache<STRONG> no code lines
  66   after the initial Graph() call will be executed</STRONG></P>
  67  <P> The design decision behind this is that your image script code never
  68   has to include anything special to make full use of the cache. It will
  69   just automatically work.</P>
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