CF7 checkbox is passed as array instead of URL

[arnelap]

Here’s a var_dump of the $data variable from the mc4wp_integration_contact-form-7_data hook:

array(4) {
["FNAME"]=>
string(5) "First"
["LNAME"]=>
string(4) "Last"
["EMAIL"]=>
string(14) "test@xxxxx.com"
["CHECKBOX1"]=>
array(1) {
[0]=>
string(4) "opt1"
}
}

And:

ERROR: Contact Form 7 > MailChimp API Error: Bad Request. The resource submitted could not be validated.

• merge_fields.CHECKBOX1 : Data did not match any of the schemas described in anyOf.

Please notify: https://wordpress.org/support/topic/sending-cf7-checkbox-fields-to-a-mailchimp-list/

[arnelap]

MailChimp doesn't really allow checkboxes (multiple values for 1 field).

You can use this filter to "join" the data in the array and send it in on 1 line.

add_filter( 'mc4wp_integration_contact-form-7_data', function( $data ) {
   $data['CHECKBOX1'] = join( ';', $data['CHECKBOX1'] );
   return $data;
});

Of course similar technique is possible to set the field in MailChimp to anything else you like based on the data your checkbox returns.