Issues in validating custom code in Contact Form 7 - php

Question

I'm trying to implement a text field validation for field name VoucherNumber that requires the code to be in a certain pattern which is 'WWV-'followed by 4 numbers.
I was successfully able to implement this on google docs using the following expression ^[W]WV-[0-9][0-9][0-9][0-9].
I researched through various answers and attempted to add this code in functions.php but it didn't work. It would just show that the form is being sent (spinning wheel) but it would not be sent even after 5 minutes.
add_filter( 'wpcf7_validate_text*', 'validate_voucher_number', 20, 2 );
function validate_voucher_number( $result, $tag ) {
$tag = new WPCF7_FormTag( $tag );
if ( 'VoucherNumber' == $tag->name ) {
$VoucherNumber = isset( $_POST['VoucherNumber'] ) ? trim( $_POST['VoucherNumber'] ) : '';
if ( ! preg_match ( "^[W]WV-[0-9][0-9][0-9][0-9]" , $VoucherNumber) ){
$result->invalidate( $tag, "Voucher number is invalid" );
}
}
return $result;
}

Answer 1

Just make sure that your field name is VoucherNumber and try this code :
add_filter( 'wpcf7_validate_text', 'vouchervalidation', 20, 2 );
function vouchervalidation( $result, $tag ) {
if ( 'VoucherNumber' == $tag->name ) {
$VoucherNumber = isset( $_POST['VoucherNumber'] ) ? trim( $_POST['VoucherNumber'] ) : '';
if ( ! preg_match ( "^[W]WV-[0-9][0-9][0-9][0-9]" , $VoucherNumber) ){
$result->invalidate( $tag, "Voucher number is invalid" );
}
}
return $result;
}