Error in PHP code to construct URL

I need to fix this URL redirect in header

$siteurl = http://myfirstsite.com
$siteurl2 = http://mysecondsite.com

<a href="<?php ech开发者_如何学Co if (strstr ($_SERVER["REQUEST_URI"], "hus")) {
    echo $siteurl;
} else {
    echo $siteurl2;
}."/".ereg_replace(" ", "-", $show_wallpaper["caturl"])."-".$show_wallpaper["categoryid"]."-"."1.php"; ?>">

It throws an error now.

You are concatenating against the braces of an if block {}. Instead, echo:

<a href="<?php echo if (strstr ($_SERVER["REQUEST_URI"], "hus")) {
    echo $siteurl;
} else {
    echo $siteurl2;
}
echo "/".ereg_replace(" ", "-", $show_wallpaper["caturl"])."-".$show_wallpaper["categoryid"]."-"."1.php"; 
?>">

First off, don't use ereg functions. They're deprecated. Use the preg functions instead.

preg_replace('/ /', '-', ...);

Beyond that, the fix is trivial:

if (...) {
   header('Location: ' . $siteurl . preg_replace(...));
} else {
   header('Location: ' . $siteurl2 . preg_replace(...));
}