Validate US ZIP Code with Zippopotamus and Contact Form 7

functions.php

<?php
/**
 * Functions
 *
 * @package      Twenty Twenty Child
 * @since        1.0
 * @link         https://rotsenacob.com
 * @author       Rotsen Mark Acob <rotsenacob.com>
 * @copyright    Copyright (c) 2020, Rotsen Mark Acob
 * @license      http://opensource.org/licenses/gpl-2.0.php GNU Public License
 *
*/

// Validate US ZIP Code Format
function validate_zipcode( $zipcode ) {
  return preg_match( '/^[0-9]{5}(?:-[0-9]{4})?$/i', $zipcode ); // @link https://www.oreilly.com/library/view/regular-expressions-cookbook/9781449327453/ch04s14.html
}

add_filter( 'wpcf7_validate_text', 'tc_validate_text', 20, 2 );
add_filter( 'wpcf7_validate_text*', 'tc_validate_text', 20, 2 );

function tc_validate_text( $result, $tag ) {
  $type = $tag['type'];
  $name = $tag['name'];
  $value = $_POST[$name];

  if ( $name == 'zipcode' ) {
    if ( validate_zipcode( $value ) ) {
      
    } else {
      $result->invalidate( $tag, wpcf7_get_message( 'invalid_zip_code' ) );
    }
  }

  return $result;
}

// Display Custom Messages
add_filter( 'wpcf7_messages', 'tc_wpcf7_messages' );
function tc_wpcf7_messages( $messages ) {
  return array_merge( $messages, array(
    'invalid_zip_code' => array(
      'default' => __( 'Invalid US ZIP Code, ZIP Code must have 5 digit numbers.' )
    )
  ) );
}

// Intercept form data to validate zip codes with Zippopotamus API before sending
add_filter( 'wpcf7_before_send_mail', function( $form, &$abort, $submission ) {
  if ( $abort === TRUE ) {
    return;
  }

  $data = $submission->get_posted_data();

  $zipcode = sanitize_text_field( $data['zipcode'] );

  $response = wp_remote_get( esc_url_raw( 'https://api.zippopotam.us/us/' . $zipcode ) );
  $body = wp_remote_retrieve_body( $response );
  $result = json_decode( $body, true );

  if ( is_wp_error( $response ) || empty( $result ) ) {
    $abort = TRUE;
    
    $submission->set_response('You entered an invalid USA ZIP code');
    $submission->set_status('api_failed');
  }
}, 10, 3 );