e-baker

I am attempting to send invoice/client details to an external API every time an invoice is marked paid. I've created a simple script in an effort to capture the actual variables that are being passed. Here's the problem: it appears the hook is not firing no matter the invoice amount. add_hook('InvoicePaid', 5, function($vars) { $output = "This is the output of the file: \n"; $output .= print_r($vars, true); $file = fopen( "invoicepayment.log", "w" ); fwrite( $file, $output ); fclose( $file );}); I've tried searching but have had no success.