why we get 0 for both conditions in shell scripting.?

[rahulvishwa]

#!/bin/bash

str3=""

if [ -z $str3 ] ; then

echo " \$? = $? "

fi

if [ -n $str3 ]
then
echo " \$? = $? "
fi

exit 0

output:-
$? = 0
$? = 0

why we get 0 for both conditions?
I am using FC15.

[giulix]

You have to double-quote the variable or use the [[ ... ]]] construct