I am implementing a website with Wordpress, but my website is not supported in Internet Explorer 8.
Is there any code I can use so that any IE8 users will be redirected to another page?
I know you specified PHP, but here's a HTML/JS solution:
<!--[if IE]>
<script type="text/javascript">
window.location = "http://www.google.com/";
</script>
<![endif]-->
Taken from this answer.
If you specifically only want to redirect IE 8 users, change <!--[if IE]>
to <!--[if IE 8]>
.