Understanding where users drop off in your osCommerce store’s purchase journey is critical for Conversion Rate Optimization (CRO). GA4’s Exploration reports and enhanced ecommerce events—when combined strategically via Google Tag Manager—can provide powerful, actionable funnel insights.
In this article, you’ll learn how to implement Purchase Funnel Tracking and perform in-depth GA4 funnel analysis tailored for osCommerce.
🧰 Prerequisites
- Google Tag Manager installed on osCommerce
- GA4 Configuration Tag already published
- Enhanced Ecommerce Events implemented (
view_item,add_to_cart,begin_checkout,purchase) - Access to
checkout_success.phpand other relevant templates
🎯 Goals of Funnel Analysis
- Identify drop-offs from product view → add to cart → checkout → purchase
- Segment funnels by device, product category, source/medium
- Attribute purchase values accurately
- Improve CRO through data-backed insights
🛒 Step 1: Define GA4 Funnel Events for osCommerce
| Funnel Step | GA4 Event | Triggered On |
|---|---|---|
| Product View | view_item |
Product detail page |
| Add to Cart | add_to_cart |
Add to cart click |
| View Cart | view_cart |
Cart page load |
| Begin Checkout | begin_checkout |
Checkout page load (Step 1) |
| Add Shipping Info | add_shipping_info |
Shipping page or step 2 |
| Purchase | purchase |
Order success / thank-you page |
🧠 Step 2: Data Layer Push on Key Pages in osCommerce
Product Page →view_item
In product_info.php:
<script>
window.dataLayer = window.dataLayer || [];
dataLayer.push({
event: "view_item",
ecommerce: {
currency: "USD",
value: <?= $product['price'] ?>,
items: [{
item_id: "<?= $product['model'] ?>",
item_name: "<?= $product['name'] ?>",
item_category: "<?= $product['category'] ?>",
price: <?= $product['price'] ?>,
quantity: 1
}]
}
});
</script>Add to Cart → add_to_cart
In your “Add to Cart” button (usually in product_info.php or JS handler):
<button class="btn btn-primary add-to-cart-btn"
data-id="<?= $product['model'] ?>"
data-name="<?= $product['name'] ?>"
data-price="<?= $product['price'] ?>"
onclick="addToCartGTM(this)">
Add to Cart
</button>
<script>
function addToCartGTM(elem) {
window.dataLayer = window.dataLayer || [];
dataLayer.push({
event: "add_to_cart",
ecommerce: {
currency: "USD",
value: parseFloat(elem.dataset.price),
items: [{
item_id: elem.dataset.id,
item_name: elem.dataset.name,
price: parseFloat(elem.dataset.price),
quantity: 1
}]
}
});
}
</script>Checkout Page → begin_checkout
In checkout_shipping.php or checkout.php:
<script>
dataLayer.push({
event: "begin_checkout",
ecommerce: {
currency: "USD",
items: <?= json_encode($cart_items_array); ?>
}
});
</script>Order Success Page → purchase
In checkout_success.php:
<script>
dataLayer.push({
event: "purchase",
ecommerce: {
transaction_id: "<?= $order['id'] ?>",
value: <?= $order['total'] ?>,
currency: "USD",
items: <?= json_encode($order['products']) ?>
}
});
</script>🏷️ Step 3: Create GA4 Event Tags in GTM
For each event (view_item, add_to_cart, begin_checkout, purchase):
- Tag Type: GA4 Event
- Event Name: Matches GA4’s ecommerce event names
- Parameters:
value→{{DL - ecommerce.value}}currency→{{DL - ecommerce.currency}}items→{{DL - ecommerce.items}}
- Trigger: Custom Event with name matching your
eventpush (e.g. add_to_cart)
✅ Step 4: Validate Events
Use:
- GTM Preview Mode to validate triggers
- GA4 DebugView to check real-time event data
- Tag Assistant to verify event parameter accuracy
📈 Step 5: Create Funnel Exploration Report in GA4
- Go to GA4 → Explore → Funnel Exploration
- Steps:
- view_item
- add_to_cart
- begin_checkout
- purchase
- Use custom dimensions (e.g.,
item_category,device_category, orsource/medium) - Filter to only non-bounced sessions for better conversion visibility
🧪 Optional Enhancements
Track Intermediate Steps
Add these events for deeper funnel tracking:
view_cart(onshopping_cart.php)add_shipping_info(after shipping selection)add_payment_info(after payment selection)
Example:
dataLayer.push({
event: "add_shipping_info",
ecommerce: {
items: <?= json_encode($cart_items_array); ?>
}
});🎯 CRO Tips Based on Funnel Data
| Insight | Actionable Fix |
|---|---|
Low add_to_cart after view_item |
Improve product copy, images, CTAs |
Drop after begin_checkout |
Simplify checkout forms, reduce steps |
Low purchase conversion |
Enable trust badges, optimize page speed |
| Mobile drop-offs | Improve mobile UX and load time |
📌 Summary
You now have a fully customized GA4 purchase funnel for osCommerce using GTM:
- Cleanly structured Enhanced Ecommerce events
- GA4 Funnel Exploration reports
- In-depth drop-off analysis
- Actionable CRO insights
🔄 What’s Next?
- Integrate server-side GTM for enhanced attribution
- Use predictive audiences in GA4 to retarget abandoners
- Combine funnel insights with A/B testing tools like VWO or Google Optimize (if re-enabled)