PHP

Monitor and Cancel a Running DKIM Operation

Demonstrates the Chilkat Dkim.HeartbeatMs and Dkim.AbortCurrent properties, which monitor and cancel a long-running operation such as a DNS public-key lookup. HeartbeatMs sets how often an AbortCheck event fires, and AbortCurrent requests cancellation.

Background: Most Dkim work is instant, but anything touching DNS can stall on a slow or unresponsive server. HeartbeatMs makes the object emit a periodic AbortCheck callback during such calls so an application stays responsive and can show progress, and AbortCurrent — set from that callback or from another thread — breaks a blocked synchronous call out early. Together they turn an otherwise uninterruptible operation into a cancellable one.

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Chilkat2 PHP

<?php

use Chilkat2\Dkim;

// Demonstrates the Dkim properties HeartbeatMs and AbortCurrent, which monitor and cancel a
// long-running operation such as a DNS public-key lookup.

$dkim = new Dkim();

// Fire an AbortCheck event callback every 100 ms during method calls.  In programming languages
// where Chilkat supports event callbacks, the callback can request cancellation.
$dkim->HeartbeatMs = 100;

// AbortCurrent may be set to true to request cancellation of a running operation.  It is
// typically set from another thread, or from within an AbortCheck callback.  Setting it false
// here ensures the operation is not pre-emptively aborted.
$dkim->AbortCurrent = false;

// PrefetchPublicKey performs a synchronous DNS lookup, which HeartbeatMs monitors and
// AbortCurrent can cancel.
try {
    $dkim->PrefetchPublicKey('myselector', 'example.com');
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo "Public key prefetched.\n";