Conditional Statements
Apache allows you to include only
select portions of a server document using conditional statements.
These conditional statements are based on the value of server-side
variables initialized earlier using the SSI set
command. The Apache flow-control statements allow you to effectively
customize a document without adding more complex CGI programs to
perform the same task.
There are four Apache flow-control statements:
<!--#if expr="expression" --> <!--#elif expr="expression"--> <!--#else--> <!--#endif-->
Each works as you would expect from an ordinary scripting language.
Note that each if
must have a closing
endif
server-side statement. For example:
<!--#if expr="$myvar=activated" --> <B>The variable appears to be activated</B> <!--#elif expr="$myvar=inactive"--> <B>The variable appears to be inactive</B> <!--#else--> <B>The variable has an unknown value</B> <!--#endif-->
Table 13-2 shows
the allowed expressions, where the order of operations is as expected
in a traditional programming language. Note that in some cases,
var2 is allowed to be an
egrep
-based regular expression if it is surrounded
by slashes (/
) on both sides.
Table 13-2. XSSI conditional expressions
Expression |
Meaning |
---|---|
var |
True if the variable is not empty |
var1=var2 |
True if the variables match |
var1!=var2 |
True if the variables do not match |
var1<var2 |
True if the first variable is less than the second |
var1<=var2 |
True if the first variable is less than or equal to the second ... |
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