how to set 404 page in php webserver 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: php set 404 page

ErrorDocument 400 /400.phpErrorDocument 401 /401.phpErrorDocument 403 /403.phpErrorDocument 404 /404.php #Don't re-add this lineErrorDocument 500 /500.php