How to set a delay?

[retropunk]

I have this script from a PHP for Flash book.
I am trying to use it to send out a newsletter to a mailing list I have. It is sort of working but I know that all the emails don't get sent. If I have only a few addresses in there it works perfect. If I put like 600, it freaks out! It seems to stop somewhere in the middle of the list and loop back to the top so 2 emails get sent to the addresses. I think the script is trying to send out all the emails at once. I would like to set a delay between each sent email so the server doesn't get hit so hard.
Any ideas?

<?

function sendEmail ($mailSubject, $mailBody) {
// Register global variables
global $subsFile;

// Set up reply address for mailing list
$mailFrom = "Kylie Ireland Newsletter <[e-mail]";

// Ensure that subject and body of email have
// automatically inserted escape slashes removed
$mailSubject = stripslashes($mailSubject);
$mailBody = stripslashes($mailBody);

// Attempt to read subscriber file
$subscribers = file($subsFile);

// If file open failed...
if (!$subscribers) {
    // Output error information and quit
    print "Couldn't open subscriber file or no subscribers listed";
    exit;
}

// For each subscriber line...
foreach($subscribers as $subscriber) {
    // split subscriber info into array
    $info = explode('|', $subscriber);

    // Assign array to meaningful variable name
    $name = $info[0];
    $email = $info[1];
    $joined = $info[2];

    // Build to address including subscriber name
    $mailTo = "$name <$email>";

    // Send email to
    mail($mailTo, $mailSubject, $mailBody, "From: " . $mailFrom);
}

print "Email sent to all subscribers";

}

?>

[crusty_php]

you can use the sleep(seconds) function for seconds or usleep(microseconds)

[tomhath]

You could try inserting a "sleep" every 50 or so iterations. From the manual:

void sleep (int seconds)

The sleep function delays program execution for the given number of seconds.