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Retrieving Variables

The previous page showed how MapServer's behavior can be influenced by sending CGI variables to it. This page shows how the results can be processed in
. When finished, MapServer sends back its results via the template file. To see how this works, we'll have a closer look at the template file
. I didn't say so before, but it is this file that is put in the window when a MapServer request returns to the browser. Mapserver replaces everything between square brackets with its computed results. A description of every variable that can be put in square brackets is in the
.
The most important template variable is undoubtedly [img]. It is replaced by the URL of the map image produced by MapServer. In the template file I put it at the physical top of the page:
<img src=[img] style="position:absolute;top:0;left:0">
When using MapClient, allmost all other return variables are put in hidden variables within a form. In this examples I used three of them, to get the actual extent, size and scale of the returned map. The form in the template file looks like this:

    <form>
    <input type=hidden name=mapext value="[mapext]">
    <input type=hidden name=scale value="[scale]">
    <input type=hidden name=mapsize value="[mapsize]">
    </form>

Every variable has a name and a value. The values are between brackets, so MapServer replaces them by the computed values. The win method "getReturnedVar()" gets the value of a named hidden variable in the first form within the window. In the HTML file, the function getVars() uses this method to get the values from the hidden variables; it puts these into the three textboxes via their JavaScript/DOM variables.
Note that the values change when the window is resized.