Fix Contact Us website form in PHP 7.0

My client has a static website in PHP and Current PHP version is 5.6. Currently he is using PHP 5.6 and PHP contact us website form is working fine with Google reCAPTCHA. The contact us form does not use any database to store the user data or to send an email. It uses 3 pages and 3 steps. The Contact us form page 1.<<== User inputs data, all fields are mandatory to and with valid format. The form moves the user to Page 2/Step 2 second page to validate the form fileds and to generate ERROR and also asks for Google reCAPTCHA verification as well. The form moves the user to thank you page and send the user data via email to an e-mail address. This only works if every thing is trun other wise click on back button and return back to the first page. The contact us online web site form uses validation in PHP (Server side validation) and validate all form fields using PHP. There is no input fields validation at user end. So, it does not matter what web browser a customer is using the form validation works fine. The client is looking forward to switch over to PHP 7.0 and when he did the contact us form stopped working. So, need some one expert in PHP 7 to fix the contact us form. Note: You will not get FTP or Filemanager access. You need to send the fixed PHP 3 pages script to me and I will upload it. :: Terms of payment :: If we award you the project then we will place 100% project Money inside a milestone. Once you fully complete the work then you we will release the 100% full payment. We always pay and you can check out our profile for past projects.