passing values in url..second page checking for null

[ism409]

Hello I am new to php. here is my problem.
I am passing a value in the url for display logic.
There is a chance that the request will not contain a value.
how do I check for null.. When I initialize the variable to "".. it always has that value(makes sense) How can I overide this with values for the request? If I do not initalize the variable I expect and the request variable is null it blows up.. Any thoughts?

In JSP I can initialize the var then overide like so:
URL:
/page2.jsp?urlValue=foo

Page 2:
<%
String a = "";
a = request.getParameter("urlValue");
%>

thanks in advance..

[pnoeric]

well, if the url is /page.php?f=test
but other times the query isn't there (so 'f' isn't set)

then your PHP script can just be...

$f = $_GET['f'];  // get query, if any
if (strlen($f)) { /* 'f' is set */ } else { /* 'f' is not set */ }

hope this helps,
Eric

[sarahk]

Use the isset() command eg isset($urlValue) which returns a boolean. Then just check how your setup lets you get the values from the url.

[ism409]

Nice!
Thanks guys.. this is exactly what I needed..
cheers!