Sending emails using Socket 4_PHP Tutorial

Implementation of send_mail class
Now let’s introduce the send mail class I wrote. With the above preparatory knowledge, the following is the implementation.
Member variables of the class
var $lastmessage; //Record the last response message returned
var $lalastact; //The last action, in string form
var $welcome; //Used in HELO Later, users are welcome
var $debug; //Whether to display debugging information
var $smtp; //smtp server
var $port; //smtp port number
var $fp; //socket Handle
Among them, $lastmessage and $lastact are used to record the last response information and the executed command. When an error occurs, the user can use them. For testing needs, I also defined the $debug variable. When its value is true, some execution information will be displayed during the running process, otherwise there will be no output. $fp is used to save the opened socket handle.
Class construction
function send_mail($smtp, $welcome="", $debug=false)
{
if(empty($smtp)) die("SMTP cannt be NULL!" );
$this-$#@62;smtp=$smtp;
if(empty($welcome))
{
$this-$#@62;welcome=gethostbyaddr("localhost ");
}
else
$this-$#@62;welcome=$welcome;
$this-$#@62;debug=$debug;
$this-$ #@62;lastmessage="";
$this-$#@62;lastact="";
$this-$#@62;port="25";
}
This The constructor mainly completes the determination and setting of some initial values. $welcome is used in the HELO directive to tell the server the user's name.
The HELO command requires a machine name, but it can be used without it. If the user does not provide $welcome, the local machine name is automatically searched.