<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
// define variables and set to empty values
$firstNameErr = $emailErr = $lastNameErr = $passwordErr = $phoneNumberErr = "";
$email = $firstName = $lastName = $password = $phoneNumber = "";

if ($_SERVER["REQUEST_METHOD"] == "POST") {
  if (filter_var($_POST["email"]),FILTER_VALIDATE_EMAIL) {
    $emailErr = "Email is valid";
  } else {
    $emailErr = "Email is invalid";
  }

  if (filter_var($_POST["password"])) {
    $passwordErr = "Password is valid";
  } else {
    $passwordErr = "Password is invalid";
  }

  if (filter_var($_POST["firstName"])) {
    $firstNameErr = "First Name is valid";
  } else {
    $firstNameErr = "First Name is invalid";
  }

  if (filter_var($_POST["lastName"])) {
    $lastNameErr = "Last Name is valid";
  } else {
    $lastNameErr = "Last Name is invalid";
  }

  if (filter_var($_POST["phoneNumber"])) {
    $phoneNumberErr = "Phone Number is valid";
  } else {
    $phoneNumberErr = "Phone Number is invalid";
  }
}
?>