how to set 404 page in php on server code example

Example 1: how to check website 404 status in php

<?php
$url = 'http://google.com';

if(@file_get_contents($url)){
	
	echo "Website is up";
	
} else {
	
	echo "Website is down";
	
}

?>

Example 2: how to create 404 page in php website

ErrorDocument 404 /404page.html