I have a registration form which sends confirmation email to the new user. i also want the same email to be sent to all registered users.

I have a table containing all registered members email and i need to inform all of them of the new user.

This is what i have so far and i need help in achieving this.

<?php
//define the receiver of the email
$to = 'youraddress@example.com';
//define the subject of the email
$subject = 'Test email';
//define the message to be sent. Each line should be separated with \n
$message = "Hello World!\n\nThis is my first mail.";
//define the headers we want passed. Note that they are separated with \r\n
$headers = "From: webmaster@example.com\r\nReply-To: webmaster@example.com";
//send the email
$mail_sent = @mail( $to, $subject, $message,$serder, $headers );
//if the message is sent successfully print "Mail sent". Otherwise print "Mail failed"
echo $mail_sent ? "Mail sent" : "Mail failed";
?>

You could select all User email address and create an array.

Then use the array in the BCC field (that way no one gets other peoples email address')

You can just submit the array? I'm not sure about this but you can separate the email addresses with a "," for multiple recipients.

And if they email addresses should remain as private, BCC as Squidge suggested.