woocommerce-set-minimum-quantity-per-product-before-checking-out-final.php

<?php

// Set minimum quantity per product before checking out

function razorfrog_set_min_qty_per_product() {
	// Only run in the Cart or Checkout pages
	if( is_cart() || is_checkout() ) {
		// Product Id and Min. Quantities per Product
		$product_min_qty = array(
			20 => 100,
			30 => 100,
			40 => 100,
			50 => 100,
		);

		// Will hold information about products that have not
		// met the minimum order quantity
		$bad_products = array();

		// Loop through the products in the Cart
		foreach( wc()->cart->cart_contents as $product_in_cart ) {
			$product_id = $product_in_cart['product_id'];

			// If there is a minimum quantity for the product and the cart item is below such quantity, add the cart item's product to the "bad" list
			if( isset( $product_min_qty[$product_id] ) && ( $product_in_cart['quantity'] < $product_min_qty[$product_id] ) ) { $bad_products[] = array( 'id' => $product_id,
					'in_cart' => $product_in_cart['quantity'],
					'min_req' => $product_min_qty[$product_id],
				);
			}
		}

		// Time to build our error message to inform the customer about the minimum quantity per order.
		if( !empty( $bad_products ) ) {
			// Lets begin building our message
			$message = '<strong>A minimum quantity per product has not been met.</strong>
';
			foreach( $bad_products as $bad_product ) {
				// Append to the current message
				$message .= get_the_title( $bad_product['id'] ) .' requires a minimum quantity of '
						 . $bad_product['min_req']
						 .' lbs. You currently have: '. $bad_product['in_cart'] .'
';
			}
			wc_add_notice( $message, 'error' );
		}
	}
}
add_action( 'woocommerce_check_cart_items', 'razorfrog_set_min_qty_per_product' );

?>