send email on mysql db update

This thread shows @kevinwood was iterating a resultset and using PHP's mail() while @nav33n suggested collecting addresses then looping with foreach. The code in the original posts eventually worked, but a few common pitfalls can silently make a loop send only one effective message or report only one address. The notes below explain what to check and a more reliable approach.

Common causes and checks:

• Header line endings: email headers must use CRLF (\r\n). Mixing PHP_EOL and \r\n or adding extra newlines can terminate headers early and confuse the MTA. Standardize on \r\n for header lines.
• BCC vs individual sends: adding a BCC for each recipient while also addressing the message to them is redundant. Decide whether to send one message with a BCC list or send separate messages per recipient. Many deliverability issues disappear when sending individual messages via authenticated SMTP.
• mail() return and logs: check the boolean return of mail() and your mail server logs for delivery errors. Spam filters and rate limits can block many recipients.
• Reporting/counting: an echo after the loop only shows the last value — move reporting inside the loop or keep a counter. @nav33n pointed this out earlier.
• Upgrades: avoid mysql_* functions. Use mysqli or PDO and validate/clean email addresses before sending.

Recommended reliable pattern (use a mail library + SMTP). Example outline:

$pdo = new PDO(...);
$emails = $pdo->query('SELECT email FROM emails')->fetchAll(PDO::FETCH_COLUMN);
$mail = new PHPMailer\PHPMailer\PHPMailer(true);
// configure SMTP/auth here
foreach ($emails as $to) {
  $mail->clearAddresses();
  $mail->addAddress($to);
  $mail->Subject = 'Website Update';
  $mail->msgHTML($message);
  $mail->send();
}

This approach improves deliverability, makes errors visible, and scales better than raw mail() calls.