Function: wpd_get_cost_price_by_product_id

Retrieve the cost price (COGS) for a product by its ID. This is the main function for accessing product cost data.

Description

Returns the cost of goods sold (COGS) for a specific product. Checks cache first for performance, retrieves from database if needed, and applies the wpd_ai_cost_price_per_unit filter before returning.

Location

File:includes/wpd-functions.php

Line:~193

Function Signature

wpd_get_cost_price_by_product_id( $product_id )

Parameters

Return Value

Type: float

Description: The cost price per unit. Returns 0.00 if no cost set or product doesn’t exist.

Example Usage

Basic Usage

// Get cost for product ID 123
$cost = wpd_get_cost_price_by_product_id( 123 );
echo 'Product cost: $' . number_format( $cost, 2 );

Calculate Profit for Product Sale

$product_id = 456;
$sell_price = 50.00;
$quantity = 2;

$cost_per_unit = wpd_get_cost_price_by_product_id( $product_id );
$total_cost = $cost_per_unit * $quantity;
$total_revenue = $sell_price * $quantity;
$profit = $total_revenue - $total_cost;

echo sprintf( 'Selling %d units: $%s revenue, $%s cost, $%s profit', 
    $quantity, 
    number_format( $total_revenue, 2 ), 
    number_format( $total_cost, 2 ), 
    number_format( $profit, 2 ) 
);

Display Cost in Custom Location

// Add cost to product admin columns
add_filter( 'manage_edit-product_columns', 'add_cost_column' );

function add_cost_column( $columns ) {
    $columns['product_cost'] = 'Cost';
    return $columns;
}

add_action( 'manage_product_posts_custom_column', 'display_cost_column', 10, 2 );

function display_cost_column( $column, $post_id ) {
    if ( $column === 'product_cost' ) {
        $cost = wpd_get_cost_price_by_product_id( $post_id );
        echo wc_price( $cost );
    }
}

Check If Product Has Cost Set

$product_id = 789;
$cost = wpd_get_cost_price_by_product_id( $product_id );

if ( $cost > 0 ) {
    echo 'Cost is set: $' . number_format( $cost, 2 );
} else {
    echo 'No cost set for this product';
}

Bulk Cost Retrieval

// Get costs for multiple products
$product_ids = array( 100, 101, 102, 103 );
$costs = array();

foreach ( $product_ids as $product_id ) {
    $costs[$product_id] = wpd_get_cost_price_by_product_id( $product_id );
}

print_r( $costs );
// Output: Array ( [100] => 25.00 [101] => 18.50 [102] => 32.00 [103] => 0.00 )

Calculate Margin on Product Page

add_action( 'woocommerce_single_product_summary', 'display_product_margin', 25 );

function display_product_margin() {
    global $product;
    $product_id = $product->get_id();
    $cost = wpd_get_cost_price_by_product_id( $product_id );
    $price = $product->get_price();
    
    if ( $cost > 0 && $price > 0 ) {
        $profit = $price - $cost;
        $margin = ( $profit / $price ) * 100;
        
        echo '
';
        echo 'Profit Margin: ' . number_format( $margin, 1 ) . '%';
        echo ' (Cost: ' . wc_price( $cost ) . ', Profit: ' . wc_price( $profit ) . ')';
        echo '
';
    }
}

Integration with External System

// Sync cost to external inventory system
add_action( 'save_post_product', 'sync_cost_to_erp', 20 );

function sync_cost_to_erp( $product_id ) {
    $product = wc_get_product( $product_id );
    if ( ! $product ) {
        return;
    }
    
    $cost = wpd_get_cost_price_by_product_id( $product_id );
    $sku = $product->get_sku();
    
    if ( $cost > 0 && $sku ) {
        // Send to ERP API
        my_erp_api_update_product_cost( $sku, $cost );
    }
}

Performance Notes

Caching

Function uses WordPress object cache:

• Cache key:_wpd_ai_product_cost_price
• Cache group: Product ID
• Results cached until product updated

Optimization Tips

• Results are cached – safe to call multiple times for same product
• For bulk operations, costs cached after first retrieval
• Cache automatically cleared when product cost updated

Special Cases

Variable Products

For variable products (with variations):

// Parent product - returns average or default
$parent_cost = wpd_get_cost_price_by_product_id( $parent_id );

// Specific variation - returns variation-specific cost
$variation_cost = wpd_get_cost_price_by_product_id( $variation_id );

// Each variation can have different cost

Products Without Cost

// Returns 0.00 if:
// - Cost not set in product
// - Product doesn't exist
// - Product ID invalid
$cost = wpd_get_cost_price_by_product_id( 999999 );
// Returns: 0.00

Bundled Products

For product bundles:

• Returns cost of the bundle product itself
• Does NOT automatically sum child product costs
• Set bundle cost manually to sum of components

Filtering Cost Value

Cost can be filtered using wpd_ai_cost_price_per_unit:

add_filter( 'wpd_ai_cost_price_per_unit', 'modify_retrieved_cost', 10, 2 ); function modify_retrieved_cost( $cost, $product_id ) { // Your custom logic return $cost; }

See wpd_ai_cost_price_per_unit filter documentation

Debugging

// Debug cost retrieval $product_id = 123; $cost = wpd_get_cost_price_by_product_id( $product_id ); error_log( sprintf( 'Product #%d cost: $%s (Type: %s)', $product_id, number_format( $cost, 2 ), gettype( $cost ) ));

Related Functions

• wpd_get_default_cost_price_by_product_id( $product_id )– Get default cost without filters
• wpd_calculate_cost_profit_by_order( $order_id )– Calculate order profit
• wpd_get_additional_costs_by_product_id( $product_id )– Get custom product costs

Related Filters

• wpd_ai_cost_price_per_unit– Filter returned cost
• wpd_ai_custom_product_cost_options– Register custom cost types