PHP javascript issues

Hi Everybody

here is my code that want to call javascript  function in PHP but not success,

<script type="text/javascript"> function error_block(){ document.getElementById('error_display').style.display = "block"; alert('hi'); }
</script> <?php error_reporting(0); if ($_POST) { // form submitted // *** 2: Escape all form data $username = mysqli_escape_string($conn, $_POST['username']); $password = mysqli_escape_string($conn, $_POST['password']); $first_name = mysqli_escape_string($conn, $_POST['first_name']); $last_name = mysqli_escape_string($conn, $_POST['last_name']); $gender = mysqli_escape_string($conn, $_POST['gender']); $address = mysqli_escape_string($conn, $_POST['address']); $email = mysqli_escape_string($conn, $_POST['email']); $tel = mysqli_escape_string($conn, $_POST['tel']); $is_admin = mysqli_escape_string($conn, $_POST['is_admin']);

$query = mysqli_query($conn, "SELECT * FROM members WHERE username = '$username'"); 


if (mysqli_num_rows($query) > 0){
    echo "<script> error_block(); </script>";
}
else{
    $result = mysqli_query($conn, "INSERT INTO members (username, password, first_name, last_name, gender, address, email, tel, is_admin) VALUES('$username', '$password', '$first_name', '$last_name', '$gender', '$address', '$email', '$tel', '$is_admin')");
}
// *** 3: Insert record


if (!$result) {
    exit(mysqli_error($conn)); // Show SQL error and halt the program
}

redirect('member.php');

} else { ?> <form method="post" action="member.php?action=add"> <!-- *** 1: Build HTML form --> <div id="error_display">user already exist</div> <p> Username: <input type="text" name="username" id="username" /> </p> <p> Password: <input type="password" name="password" id="password" /> </p> <p> First Name: <input type="text" name="first_name" id="first_name" /> </p> <p> Last Name: <input type="text" name="last_name" id="last_name" /> </p> <p> Gender: <input type="radio" name="gender" value="M" /> M <input type="radio" name="gender" value="F" /> F </p> <p> Address: <input type="text" name="address" id="address" /> </p> <p> Email: <input type="text" name="email" id="email" /> </p> <p> Tel: <input type="text" name="tel " id="tel" /> </p> <p> Is Admin?: <input type="radio" name="is_admin" value="1" /> Yes <input type="radio" name="is_admin" value="0" /> No </p> <p> <button type="submit" name="submit">Submit</button> </p> </form> <?php } ?>

what do i need to correct in order to make the call function work?