begins-checkout.php

<script>
  var products = [];
  
  <?php 
    var products = //Array of products
    foreach ($products as $product) { ?>
    
    // Add the product to the JS array
    products.push({
      name: "<?php $product['name'] ?>",
      price: "<?php $product['price'] ?>"
    });
    
  <?php } ?>
  
  // Track the event with the product meta-data after you've got them in the array
  _veroq.push(['track', 'begins checkout', {products: products}]);
</script>