验证后仍提交数据返回 false

我一直在尝试创建一个注册表单，我已经尝试了几种方法，但我最后添加到其中的是 else if （$status = "OK"） 行。以下是我代码的一部分，请帮助我仍然是编码新手;

<?php
$surnameErr = $firstnameErr = $usernameErr = $emailErr = $passwordErr = $password1Err = "";
$surname = $firstname = $username = $email = $password = $password1 = "";
$status = "OK";
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    if (empty($_POST["surname"])) {
     $surnameErr = "Surname is required";
     $status = "NOTOK";
   } 
   else {
     $surname = test_input($_POST["surname"]);
        if (!preg_match("/^[a-zA-Z ]*$/",$surname)) {
        $surnameErr = "Only letters and white space allowed"; 
        $status = "NOTOK";
        }
   }
   if (empty($_POST["firstname"])) {
       $firstnameErr = "First Name is required";
       $status = "NOTOK";
   } 
   else {
     $firstname = test_input($_POST["firstname"]);
        if (!preg_match("/^[a-zA-Z ]*$/",$firstname)) {
            $firstnameErr = "Only letters and white space allowed";
            $status = "NOTOK";
        }
   }
   if (empty($_POST["username"])) {
     $usernameErr = "Username is required";
     $status = "NOTOK";
   } else {
     $username = test_input($_POST["username"]);
   }
   if (empty($_POST["email"])) {
     $emailErr = "Email is required";
     $status = "NOTOK";
   } else {
     $email = test_input($_POST["email"]);
     if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $emailErr = "Invalid Email format"; 
        $status = "NOTOK";
        }
   }
   if (empty($_POST["password"])) {
     $passwordErr = "Password is required";
     $status = "NOTOK";
   } 
   if (empty($_POST["password1"])) {
     $password1Err = "Repeat password to confirm";
     $status = "NOTOK";
   }
   if ($password != $password1){
       echo "<script>alert('Password does not match')</script>";
       $status = "NOTOK";
   }
    $connection = mysqli_connect("localhost", "root", "", "church") or die(mysqli_error());
    $checkuser = mysqli_query ($connection,"SELECT * FROM signup WHERE username = '$username'");
    if (mysqli_num_rows ($checkuser) > 0){
        echo "<script>alert('$username already exist in our database, please enter another one')</script>";
        $status = "NOTOK";
    }
    $checkemail = mysqli_query ($connection,"SELECT * FROM signup WHERE email = '$email'");
    if (mysqli_num_rows ($checkemail) > 0){
        echo "<script>alert('$email already exist in our database, please enter another one')</script>";
        $status = "NOTOK";
    }
    else if ($status = "OK"){
        $password=md5($password);
        $datainsert = mysqli_query ($connection, "INSERT INTO signup (surname, firstname, username, email, password) VALUES ('$surname', '$firstname','$username','$email','$password')") or die(mysqli_error());
            echo "<script>alert('Sign Up Successful!')</script>";
        }
   }   
function test_input($data) {
  $data = trim($data);
  $data = stripslashes($data);
  $data = htmlspecialchars($data);
  return $data;
}
?>