如何从php MySQL sql注入到MySQLi不脆弱的查询

im learning MySQLi in order to make my site not vulnerable to SQL injections (wich is now) but i get confuse when i was trying to "translate" my old querys to MySQLi statements, so i hope you can help me with some examples so i can get it. Thanks a lot!.im learning MySQLi in order to make my site not