I'm customizing a Woocommerce Wordpress site.

In the Woocommerce product class (class-wc-product.php) the get_price function applies a filter as follows:

function get_price() {
    return apply_filters('woocommerce_get_price', $this->price, $this);

In my functions.php I want to add a filter as follows:

add_filter('woocommerce_get_price', 'custom_price');

function custom_price($price, $product) {

When I call this I get the following PHP warning:

Warning: Missing argument 2 for custom_price()

Why is the second argument missing? Is $this not sent to the filter call?

  • Maybe apply_filters('woocommerce_get_price', … ); is called somewhere else without the second argument? Did you search for such a case?
    – fuxia
    Nov 12, 2012 at 15:10
  • It's called only once as far as I can see
    – benedict_w
    Nov 12, 2012 at 15:12

2 Answers 2


It's missing the second argument because you didn't tell WordPress you wanted it with your add_filter call. By default, actions and filters only get one argument. Try this:

add_filter('woocommerce_get_price', 'custom_price', 10, 2);

function custom_price($price, $product) {
  • Good answer Chris, exactly why I love this site. I learn something new every day.
    – Steve
    Nov 12, 2012 at 16:10
  • For the longest time I didn't even know the value for parameter 4 dictates the number of arguments to pass in. TY
    – Antony
    Feb 21, 2018 at 22:17

The warning is a result of the second argument in your function custom_price(). The filter provides only one variable on the call and I can't remember if this is the product/post ID or the price. The code docs indicate that it returns a string so I'd presume it's the price.

You can hopefully find the documentation at http://wcdocs.woothemes.com/apidocs/index.html

If you need the product at this point you'll have to use:

function custom_price( $price ) {

    global $product;


If all else fails simply echo $price to see if you can tell if it's a product ID or a price. Then adjust your code accordingly.

  • Thanks for your insights @chrisguitarguy's anwser seems to have done the trick for me.
    – benedict_w
    Nov 12, 2012 at 15:52
  • Yeah, it's certainly a more elegant solution.
    – Steve
    Nov 12, 2012 at 16:08

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