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Bobby Jack
Asked: 2011-08-02 04:17:11 +0800 CST

How do I conditionally handle undefined SSI variables using Apache?

  • 772

I want to include a header in a bunch of pages, like so:

header.html: 

<html>
  <head>
    <title>My site</title>
  </head>

To enable a page-specific title, I'm trying to use an SSI variable that I set in each page:

page1.html:

<!--#set var="TITLE" value="first page" -->
<!--#include file="header.html" -->

Then I”m modifying header.html to use that variable:

<title>My site - <!--#echo var="TITLE" --></title>

This works fine but, of course, it has the unfortunate effect that, if TITLE is not set, the result is:

<title>My site - (none)</title>

So I'm trying a variety of attempts at conditionally echoing that variable depending on whether it's none or not (e.g., <!--#if expr="TITLE != \(none\)" --> ... <!--#endif-->) …but nothing seems to work.

Seems like this would be quite a common requirement. Does anyone have a reference to a working solution?

apache-2.2 server-side-includes

3 Answers

  1. For Apache 2.4 the expressions have changed:

    <!--#if expr="-z v('CONTENT_LANGUAGE')"-->
<!--#set var="CONTENT_LANGUAGE" value="en"-->
<!--#endif-->
    • 5

  2. I've used this successfully:

    <!--#if expr="! $CONTENT_LANGUAGE" -->
<!--#set var="CONTENT_LANGUAGE" value="en" -->
<!--#endif -->
    • 1
  3. Best Answer

    OK, solved it myself. For others' reference:

    <!--#if expr="${TITLE}!=''" -->

    is the correct syntax to use. It makes sense that you don't have to check for "(none)" since the undefined text value can be configured; I just didn't realised that occurred after checking the value, not before.

    • 0