If someone knows my url of the admin page such as www.example.com/admin.php, then they will easily access the page by directly accesing that url. How to restrict this. Pleas
If you have cPanel (or a similar control panel) access, you can easily create password protected directories as well. This method uses htpasswd and htaccess files. If you set it up this way, anyone trying to access the protected directory will have to enter a user/pass. The only down side to it is that your admin files need to be in a directory of their own.