please help! thanks

4. Create a PHP file named subscribe_action.php that does the following when the form is submitted: obtain the value of each input field from the subscription form validate each input field (it exists, and it matches an appropriate regex pattern) return error messages for all validation errors, if any return a welcome message, if no errors are found append the input data to subscribe_data.txt, on a single line, if no errors are found . . . 5. Be sure that the file subscribe_data.txt also has the correct group and access control settings, so that it can be read using a web browser (.../cs312/hw2/subscribe_data.txt)