can some1 help me

[Hughra Hosting]

im writin a script that auto creats a account. so far everything works except it says cannot modify header information.

this is what i got... i left of the form, this is the php script.
also.. i use queries..ex main.php?page=order

if($sent)
{
#set variable default value
$valid=true;

#check first field is not blank
if( !$fname )
{ $errmsg.="Please enter your first name.<br />"; $valid = false; }


#check lastname field is not blank
if( !$lname )
{ $errmsg.="Please enter your last name.<br />"; $valid = false; }

#check phonenumber field is not blank
if( !$pnumber )
{ $errmsg.="Please enter your phone number.<br />"; $valid = false; }

#check address field is not blank
if( !$address )
{ $errmsg.="Please enter a street address.<br />"; $valid = false; }

#check zip field is not blank
if( !$zip )
{ $errmsg.="Please enter your zip code.<br />"; $valid = false; }

#check city field is not blank
if( !$lname )
{ $errmsg.="Please specify your city.<br />"; $valid = false; }


#check email useraddr field is not blank
if( !$useraddr )
{ $errmsg .="Please enter an email address.<br />"; $valid = false; }

#modified section with extra validation
else
{
$useraddr = trim($useraddr);
#permitted patterns for name,domain and top-level domains
$_name = "/^[-!#$%&\'*+\\.\/0-9=?A-Z^_`{|}~]+";
$_host = "([-0-9A-Z]+\.)+";
$_tlds = "([0-9A-Z]){2,4}$/i";

#check validity of email format
if( !preg_match( $_name."@".$_host .$_tlds,$useraddr ) )
{
$errmsg.="Email address has incorrect format!<br />";
$valid=false;
}
}

if( !$acctdomain )
{ $errmsg.="Please specify a domain.<br />"; $valid = false; };

if( !$acctuser )
{ $errmsg.="Please specify a username.<br />"; $valid = false; }

if( !$acctpass )
{ $errmsg.="Please specify a password.<br />"; $valid = false; }

}

#if not valid write the error mesage/s and repeat the form
if($valid!=true)
{
echo( $errmsg.$form );
}
else
$file_contents = ob_get_contents();

ob_end_clean();

setcookie( "acctplan", $acctplan, time()+3600 );
setcookie( "acctdomain", $acctdomain, time()+3600 );
setcookie( "acctpass", $acctpass, time()+3600 );
setcookie( "acctuser", $acctuser, time()+3600 );

print $file_contents;

[nybble]

You can not modify header info, that means exactly what it says.

Once you send the user output(eg. html), you can not send any more headers (Yes, this includes cookies)