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It amazes me how many developers just use something along the lines of:
if($var != '')
to check for an empty value.
Yet, if someone just hits the spacebar, $var won't be empty, and will appear OK to the above
conditional.
Whitespace has value people. For that matter, so do newlines and tabs (\n and \t,
respectively, along with a few more (consult your languages' manuals. They are, almost, the
best friends you have as a programmer).)
In PHP, use trim() to hack off whitespace, then use empty() to make sure it's, you guessed it,
not empty.
http://www.php.net/manual/function.trim.php
http://www.php.net/manual/function.empty.php
In Perl use something like:
if($var !~ /^\s*$/)
And, of course, always filter your input, when your data will be coming from an outside source,
to ensure that you'll get exactly what you're looking for.
For PHP, there are a host of terrific functions for this purpose. Check them out:
http://www.php.net/manual/ref.strings.php
For Perl (CGI), you will most certainly want to enable Taint checking. Stick the -T switch at the
top of your script/application:
#!/usr/bin/perl -T
use strict;
You'll see errors, and it's in your best interest to learn what they mean.
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