The PHP mail() function is used to send emails from inside a script.

Prototype:

boolean mail(string to, string subject, string message [, string addl_headers [, string addl_params]])

Parameter
Description
to
Required. Specifies the receiver / receivers of the email
subject
Required. Specifies the subject of the email. Note: This parameter cannot contain any newline characters
message
Required. Defines the message to be sent. Each line should be separated with a LF (\n). Lines should not exceed 70 characters
headers
Optional. Specifies additional headers, like From, Cc, and Bcc. The additional headers should be separated with a CRLF (\r\n)
parameters
Optional. Specifies an additional parameter to the sendmail program


Example:

<?php
   
    mail("client@example.com","This is a subject","This is the mail body","from:admin@example.com\r\n");

?>

Session data can be stored in four ways: 
1. Within flat failes (files), 
2. Within volatile memory (mm), 
3. Using the SQLite database (sqlite), or 
4. Through user-defined functions (user).

1. HTTP - Hyper Text Transfer Protocol
2. FTP - File Transfer Protocol
3. POP3 - Post Office Protocol
4. IMAP - Internet Message Access Protocol
5. SSH - Secure SHell

The getservbyname() function returns the port number of a specified service.

Prototype:

int getservbyname(string service, string protocol)

Example:

<?php
   echo "HTTP's default port number is: ".getservbyname("http","tcp");

?>

The fsocketopen() function establishes a connection to the resource designated by target on port.

Prototype:

resource fsockopen( string target, int port [, int erron [, string errsting [, float timeout]]])

Example:

<?php
   $http=fsockopen("www.example.com",80);
  
   $req="GET / HTTP/1.1\r\n";
   $req.="Host: www.example.com\r\n";
   $req.="Connection: Close\r\n\r\n";

  fputs($http,$req);
 
  while(!feof($http)){

      echo fgets($http,1024);

   }
fclose($http);
 
?>