Add support for currency with pronamic_pay_currency field name or option.

README.md

@@ -11,6 +11,17 @@ it requires the `pronamic_pay_amount` option:
 [number pronamic_pay_amount]
 ```
 
+## Currency
+
+Payments are created with the Euro currency by default. An ISO 4217 currency code can be provided
+using the `pronamic_pay_currency` field name or as a field option: 
+
+```
+[hidden pronamic_pay_currency "CHF"]
+
+[select select-123 pronamic_pay_currency "EUR" "CHF"]
+```
+
 ## WordPress environment for building and testing
 
 ```
@@ -35,3 +46,4 @@ skip_mail: on
 - https://wordpress.org/plugins/cf7-conditional-fields/
 - https://contactform7.com/
 - https://contactform7.com/tag-syntax/
+- https://en.wikipedia.org/wiki/ISO_4217#List_of_ISO_4217_currency_codes

src/Pronamic.php

@@ -68,7 +68,14 @@ public static function get_submission_payment( WPCF7_Submission $submission ) {
 		$submission_helper = new SubmissionHelper( $submission );
 
 		// Total.
-		$total  = new Money();
+		$currency = \strtoupper( $submission_helper->get_value_by_tag_name_or_option( 'pronamic_pay_currency' ) );
+
+		if ( '' === $currency ) {
+			$currency = 'EUR';
+		}
+
+		$total = new Money( 0, $currency );
+
 		$parser = new Parser();
 
 		$tags = $submission_helper->get_tags_with_basetype_or_name_or_option( 'pronamic_pay_amount' );