How to use .htacces to disallow external links?

for examples, my domain is abc.com, how can i use .htaccess to disallow any other external links in my site, say if there is an external domain: 123.com.

How can i let 123.com becomes my domain abc.com or something else?

tks.

 

Htaccess can't do this for you. htaccess is a request preprocessor, not a post processor.

 

how to use .htaccess to let abc.com become 123.comthen?

 

You could do somehing like :

RewriteCond %{HTTP_HOST} ^www.olddomain.com$[OR]
RewriteCond %{HTTP_HOST} ^olddomain.com$
RewriteRule ^(.*)$ http://www.newdomain.com/$1 [R=301,L] 

Code (markup):

or

redirect 301 / http://www.newdomain.com 

Code (markup):

But all these only work if you own olddomain.com (abc.com). You cannot rewrite urls that you do not own because your htaccess needs to be on that domain.

 

You have to do this via scripting (PHP) rather than .htaccess.

 

how to do via php, please?

 

I am not good in programming otherwise I provide sample code