Blind Carbon Copy
For emails. It is used to send a copy of the email to somebody without the original person receiving it knowing that you sent a copy.
 
        
                    
             
        
        
        
Answer: packets 
Explanation: 
Network navigation devices, such as routers, help data travel in bundles that are referred to as packets. As, networks that transfer the data in small packets are known as packet switching network and that packets carry the data using the internet and the protocol and each of the packet contain some information and data to navigate.
 
        
             
        
        
        
The PHP code is given below:
<h3>PHP code</h3>
if(isset($_REQUEST['login_btn'])){
        $email = filter_var(strtolower($_REQUEST['email']),FILTER_SANITIZE_EMAIL); //strtolower changes email to all lower case
        $password = strip_tags($_REQUEST['password']);
The remaining code is in the file attached.
   
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