Good little programmers define variables before 
using them, or at least before evaluating them.

  print $undefined; // E_NOTICE error

The most common use of this is:

  if ($submit) {

To check if a form submit button named submit 
has been submitted.  If not, this does indeed 
evaluate to false BUT also an error of level E_NOTICE 
is created.  So, one might do the following, 
which will never give E_NOTICE:

  if (isset($submit)) {

At any rate, the reason is your error levels 
are different.  Look up the error_reporting 

A function also controls this behavior within scripts, 
it's appropriatly named error_reporting()

So, start programming your code with error_reporting(E_ALL) 
and have fun!

Philip Olson

p.s. Although it's fairly common to create E_NOTICE all over 
the place, it's not a good idea.  More and more people are 
learning to not do that.

On Tue, 2 Apr 2002, kip wrote:

> Hi,
> As i know we don't need to define a variable before in PHP. But i have a
> very strange case. In my server, i hosted a PHP website. When i update the
> server from PHP3 to PHP4, problems came out. Most of the php pages didn't
> work and display many warnings like that :
> "Warning: Undefined variable: variable_name". In fact, nobody has changed
> the code and all of the pages are working property in PHP3 server. So, does
> anyone know what happen? I also contact the hosting company, but they said
> that everything is working fine and they don't know what problem is it.
> Thats why i have no idea how to correct it.
> Thanks.
> Kenny
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