Real time Email Vaildation in PHP

In most of the application, I've simply checked email pattern for validation. I never tried to implement whether email exists or not. Because of this lots of unnecessary records will be inserted into database.

Using PHP built-in functions (Socket programming and DNS functions) we can find out whether the provided email address is existed or not. I've got this script from ZEND IDE code snippets.

<?
/* =======================================================================
  
 ifsnow's email valid check function SnowCheckMail Ver 0.1
 
 funtion SnowCheckMail ($Email,$Debug=false)

 $Email : E-Mail address to check.
 $Debug : Variable for debugging.

 * Can use everybody if use without changing the name of function.

 Reference : O'REILLY - Internet Email Programming

 HOMEPAGE : http://www.hellophp.com

 ifsnow is korean phper. Is sorry to be unskillful to English. *^^*;;

========================================================================= */

function SnowCheckMail($Email,$Debug=false)
{
    global $HTTP_HOST;
    $Return =array(); 
    // Variable for return.
    // $Return[0] : [true|false]
    // $Return[1] : Processing result save.

    if (!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $Email)) {
        $Return[0]=false;
        $Return[1]="${Email} is E-Mail form that is not right.";
        if ($Debug) echo "Error : {$Email} is E-Mail form that is not right.<br>";        
        return $Return;
    }
    else if ($Debug) echo "Confirmation : {$Email} is E-Mail form that is not right.<br>";

    // E-Mail @ by 2 by standard divide. if it is $Email this "lsm@ebeecomm.com"..
    // $Username : lsm
    // $Domain : ebeecomm.com
    // list function reference : http://www.php.net/manual/en/function.list.php
    // split function reference : http://www.php.net/manual/en/function.split.php
    list ( $Username, $Domain ) = split ("@",$Email);

    // That MX(mail exchanger) record exists in domain check .
    // checkdnsrr function reference : http://www.php.net/manual/en/function.checkdnsrr.php
    if ( checkdnsrr ( $Domain, "MX" ) )  {
        if($Debug) echo "Confirmation : MX record about {$Domain} exists.<br>";
        // If MX record exists, save MX record address.
        // getmxrr function reference : http://www.php.net/manual/en/function.getmxrr.php
        if ( getmxrr ($Domain, $MXHost))  {
      if($Debug) {
                echo "Confirmation : Is confirming address by MX LOOKUP.<br>";
              for ( $i = 0,$j = 1; $i < count ( $MXHost ); $i++,$j++ ) {
            echo "&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Result($j) - $MXHost[$i]<BR>"; 
        }
            }
        }
        // Getmxrr function does to store MX record address about $Domain in arrangement form to $MXHost.
        // $ConnectAddress socket connection address.
        $ConnectAddress = $MXHost[0];
    }
    else {
        // If there is no MX record simply @ to next time address socket connection do .
        $ConnectAddress = $Domain;        
        if ($Debug) echo "Confirmation : MX record about {$Domain} does not exist.<br>";
    }

    // fsockopen function reference : http://www.php.net/manual/en/function.fsockopen.php
    $Connect = fsockopen ( $ConnectAddress, 25 );

    // Success in socket connection
    if ($Connect)  
    {
        if ($Debug) echo "Connection succeeded to {$ConnectAddress} SMTP.<br>";
        // Judgment is that service is preparing though begin by 220 getting string after connection .
        // fgets function reference : http://www.php.net/manual/en/function.fgets.php
        if ( ereg ( "^220", $Out = fgets ( $Connect, 1024 ) ) ) {
            
            // Inform client's reaching to server who connect.
            fputs ( $Connect, "HELO $HTTP_HOST\r\n" );
                if ($Debug) echo "Run : HELO $HTTP_HOST<br>";
            $Out = fgets ( $Connect, 1024 ); // Receive server's answering cord.

            // Inform sender's address to server.
            fputs ( $Connect, "MAIL FROM: <{$Email}>\r\n" );
                if ($Debug) echo "Run : MAIL FROM: &lt;{$Email}&gt;<br>";
            $From = fgets ( $Connect, 1024 ); // Receive server's answering cord.

            // Inform listener's address to server.
            fputs ( $Connect, "RCPT TO: <{$Email}>\r\n" );
                if ($Debug) echo "Run : RCPT TO: &lt;{$Email}&gt;<br>";
            $To = fgets ( $Connect, 1024 ); // Receive server's answering cord.

            // Finish connection.
            fputs ( $Connect, "QUIT\r\n");
                if ($Debug) echo "Run : QUIT<br>";

            fclose($Connect);

                // Server's answering cord about MAIL and TO command checks.
                // Server about listener's address reacts to 550 codes if there does not exist 
                // checking that mailbox is in own E-Mail account.
                if ( !ereg ( "^250", $From ) || !ereg ( "^250", $To )) {
                    $Return[0]=false;
                    $Return[1]="${Email} is address done not admit in E-Mail server.";
                    if ($Debug) echo "{$Email} is address done not admit in E-Mail server.<br>";
                    return $Return;
                }
        }
    }
    // Failure in socket connection
    else {
        $Return[0]=false;
        $Return[1]="Can not connect E-Mail server ({$ConnectAddress}).";
        if ($Debug) echo "Can not connect E-Mail server ({$ConnectAddress}).<br>";
        return $Return;
    }
    $Return[0]=true;
    $Return[1]="{$Email} is E-Mail address that there is no any problem.";
    return $Return;
}
?>