Variable in custom register field

[CampinCarl]

I have a field that asks for a player's steam id while registering. We have a plugin for source that tracks a player's steam id and logs it into a database with their ip address. I also have a php file that accesses that steam id and will "echo" it depending on what ip they are on. So I would like to put that variable as the default value in a custom register field.

PHP file:

<?PHP
	//GET PLAYER INFORMATION
	mysql_connect( "localhost", "protf2_servers", "password" ) or die( mysql_error() );
	mysql_select_db( "protf2_servers" ) or die( mysql_error() );

	$query = mysql_query("SELECT `steamid` FROM player_tracker WHERE `playerip`='$_SERVER[REMOTE_ADDR]'") or die(mysql_error());
	$steamid = mysql_fetch_assoc($query);
	
	echo $steamid['steamid'];
?>

V-Bulletin Plugin that includes the php file:

ob_start(); 
  require_once('/home/protf2/public_html/steamid.php'); 
  $steamid = ob_get_contents(); 
ob_end_clean(); 
vB_Template::preRegister('register',array('steamid' => $steamid));

(global_start, named "steam_id)

And when making a template, i would use {vb:raw steamid} to make that steam id variable show.