Blockchain Receive API - custom Parameters I am trying to get variables back from the callback URL, but I can't figure out how to add custom parameters correctly. This is how I have them written right now:

$newAddy = json_decode(file_get_contents("https://blockchain.info/merchant/$ID/new_address?password=$PW&amp;funding_id=$funding_id"),true);
$parseAddy = $newAddy[address];


$funding_id is the extra one that I want to add. Any suggestions?
You appear to be confusing two different blockchain's API services into one. The code snippet you provided is for their old deprecated wallet API, but your title mentioning the receive payments API is another. 

Wallet API: https://blockchain.info/api/blockchain_wallet_api
(The new version requires a local service installed via NPM)

Receive Payments API: https://blockchain.info/api/api_receive

You can add any custom parameter you would like when using the Receive Payments API just by including it as a GET within your callback URL. 

$callback_url = "yourwebsite.com/callback.php?parameter1=".$var1."&amp;parameter2=".$var2;