Webhook Notifications (Zapier, Make, n8n)

Send a JSON webhook payload on every redirect click. Connect GT Link Manager to any automation platform — Zapier, Make (Integromat), n8n, Pipedream, or your own custom endpoint. Build automated workflows triggered by link clicks: send Slack notifications, update spreadsheets, trigger email sequences, and more.

Requirements

• GT Link Manager 1.5+ installed and active
• A webhook URL from your automation platform (e.g., Zapier’s “Webhooks by Zapier” trigger, Make’s webhook module, or n8n’s webhook node)

Installation

• Add the snippet below to your theme’s functions.php or a site-specific plugin
• Replace the webhook URL with your actual endpoint
• (Optional) Set a shared secret for HMAC payload verification

The Code

<?php
/**
 * GT Link Manager - Webhook Notifications
 *
 * Sends a JSON payload to any webhook URL on every redirect click.
 * Works with Zapier, Make (Integromat), n8n, Pipedream, or any custom endpoint.
 *
 * Setup:
 * 1. Create a webhook in your automation tool (Zapier: "Webhooks by Zapier" trigger)
 * 2. Set GTLM_WEBHOOK_URL to that webhook URL
 * 3. (Optional) Set a secret for payload verification
 *
 * Payload includes: link data, target URL, referrer, user agent, timestamp.
 */

defined( 'ABSPATH' ) || exit;

// ── Configuration ────────────────────────────────────────────────────────────
define( 'GTLM_WEBHOOK_URL',    'https://hooks.zapier.com/hooks/catch/your-id' ); // Webhook endpoint
define( 'GTLM_WEBHOOK_SECRET', '' ); // Shared secret for HMAC signature (optional)
// ─────────────────────────────────────────────────────────────────────────────

add_action( 'gtlm_before_redirect', 'gtlm_webhook_send', 10, 4 );

/**
 * Send a webhook payload on every redirect.
 *
 * @param array  $link       Link data.
 * @param string $target_url Destination URL.
 * @param int    $status     HTTP status code.
 * @param array  $headers    Response headers.
 */
function gtlm_webhook_send( array $link, string $target_url, int $status, array $headers ): void {

	if ( str_contains( GTLM_WEBHOOK_URL, 'your-id' ) ) {
		return; // Not configured yet.
	}

	$payload = [
		'event'      => 'link_click',
		'timestamp'  => gmdate( 'c' ),
		'site_url'   => home_url(),
		'link'       => [
			'id'          => (int) $link['id'],
			'name'        => $link['name'] ?? '',
			'slug'        => $link['slug'] ?? '',
			'short_url'   => home_url( sanitize_text_field( $_SERVER['REQUEST_URI'] ?? '' ) ),
			'target_url'  => $target_url,
			'redirect'    => $status,
			'category_id' => (int) ( $link['category_id'] ?? 0 ),
			'tags'        => $link['tags'] ?? '',
		],
		'visitor' => [
			'referrer'   => sanitize_text_field( $_SERVER['HTTP_REFERER'] ?? '' ),
			'user_agent' => sanitize_text_field( $_SERVER['HTTP_USER_AGENT'] ?? '' ),
		],
	];

	$body = wp_json_encode( $payload );

	$request_headers = [
		'Content-Type' => 'application/json',
	];

	// Add HMAC signature for payload verification if secret is set.
	if ( ! empty( GTLM_WEBHOOK_SECRET ) ) {
		$request_headers['X-GTLM-Signature'] = hash_hmac( 'sha256', $body, GTLM_WEBHOOK_SECRET );
	}

	wp_remote_post(
		GTLM_WEBHOOK_URL,
		[
			'body'     => $body,
			'headers'  => $request_headers,
			'blocking' => false,
			'timeout'  => 2,
		]
	);
}

How It Works

• Hooks into gtlm_before_redirect to fire on every redirect click
• Sends a structured JSON payload with: event type, timestamp, site URL, full link data, and visitor info
• Link data includes: ID, name, slug, short URL, target URL, redirect status, category, and tags
• Visitor data includes: referrer and user agent
• Optionally signs the payload with HMAC-SHA256 via the X-GTLM-Signature header for verification
• Non-blocking request ('blocking' => false) — no redirect delay

Configuration Notes

The GTLM_WEBHOOK_SECRET is optional but recommended for production use. When set, the payload is signed with HMAC-SHA256 and the signature is sent in the X-GTLM-Signature header. Your receiving endpoint can verify the signature to ensure the webhook is authentic.

To verify the signature on the receiving end, compute hash_hmac('sha256', $raw_body, $secret) and compare it to the header value.