In the .htaccess file you should create a code similar to this:
RewriteEngine On
ErrorDocument 404 /404.php
Note: There are many options and different structure types and different ways to redirect to a specific error page either using .htaccess or PHP strong> natively among others.
Somewhat more advanced to the different redirection errors.
ErrorDocument 404 http://example.com/404/
ErrorDocument 500 http://example.com/500/
# or map them to one error document:
# ErrorDocument 404 /pages/errors/error_redirect.php
# ErrorDocument 500 /pages/errors/error_redirect.php
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} ^/404/$
RewriteRule ^(.*)$ /pages/errors/404.php [L]
RewriteCond %{REQUEST_URI} ^/500/$
RewriteRule ^(.*)$ /pages/errors/500.php [L]
# or map them to one error document:
#RewriteCond %{REQUEST_URI} ^/404/$ [OR]
#RewriteCond %{REQUEST_URI} ^/500/$
#RewriteRule ^(.*)$ /pages/errors/error_redirect.php [L]
The .htaccess of the previous example has several examples in it. You can use the following as the generic redirect script to replace 404_redirect.php previously.
error_redirect.php
<?php
$error_url = $_SERVER["REDIRECT_STATUS"] . '/';
$error_path = $error_url . '.php';
if ( ! file_exists($error_path)) {
// this is the default error if a specific error page is not found
$error_url = '404/';
}
header('Location: ' . $error_url);
exit;
?>
Source SO English