open new URL in if statement

How do I automatically open a new URL based on a condition being met ? i.e. what should the line 'open URL ... 'state?

Note - previous code includes html / text output; therefore header method doesn't work.
This is for a password scheme.

// previous code

if a == b {
open URL "http://www.url.com" ;
}else{
echo "Incorrect choice";
}

// additional code

this should do it

if ($a==$b)
{
echo "<meta http-equiv="refresh" content="0;url=http://www.whatever.com/">";
}else{
echo "Incorrect choice";
}

hth

------------------
cheers

thanks timbo; but have a question;

why doesn't php see the 2 //'s in the url as a start of a comment? My editor (homesite) saw them as a start of a comment, i saw them as a comment, so i kept trying to them out and it didn't work. It did work your way.

thanks again

For php to see them as a start of a comment they must be preceded by <? or ; with nothing but whitespace (spaces,n,t,etc) between.

gotcha - thanks