I'm trying to make a simple form that can check if the name and email are empty and not in the proper format
here's my code
<!DOCTYPE html>
<html>
<head>
    <title>Register</title>
</head>
<body>
<?php
include ('connect.php');
    $first = $_POST['fname'];
    $last = $_POST['lname'];
    $email = $_POST['email'];
if (isset($_POST['submit']))
{
    if ($first == '' || $first == ' ' || $last == '' || $last == ' '|| $email == "" || $email == " " || !preg_match("/^[a-zA-Z]*$/", $first) || !preg_match("/^[a-zA-Z]*$/", $last) || !filter_var($email, FILTER_VALIDATE_EMAIL))
    {
        if ($first == '' || $first == ' ' )
        {
            $fnameErr = "First name is required!";
        }
        else
        { 
            if(!preg_match("/^[a-zA-Z]*$/", $first))
            {
                $fnameErr = "Only letters are allowed!";
            }
            else
            {
                $fnameErr = "";
            }
        }
        if($last == '' || $last == ' ')
        {   
            $lnameErr = "Last name is required!";
        }
        else
        {
            if(!preg_match("/^[a-zA-Z]*$/", $last))
            {
                $lnameErr = "Only letters are allowed!";
            }
            else
            {
                $lnameErr = "";
            }
        }
        if ($email == "" || $email == " ")
        {
            $emailErr = "Email is required!";
        }
        else
        {
            if(!filter_var($email, FILTER_VALIDATE_EMAIL))
            {
                $emailErr = "Invalid email!";
            }
            else
            {
                $emailErr = "";
            }
        }
    }
    else
    {
        echo "<br>You've successfully created your account<br>";
        mysql_query("INSERT into register SET FNAME='$first', LNAME='$last', EMAIL='$email'")
        or die(mysql_error());
    }
}
?>
<h2 align="center">Registration Form</h2>
<form action="" method="POST" align='center'>
    <p>First Name:
    <input type="text" name="fname"> <?php echo $fnameErr; ?>
    <br>
    <p>Last Name:
    <input type="text" name="lname"> <?php echo $lnameErr; ?>
    <br>
    <p>  
    Email:
       
    <input type="text" name="email"> <?php echo $emailErr; ?>
    <br><br>
    </p>
    <input type="submit" value="Submit" name="submit">
</form>
</body>
</html>
I already declared a variables, but when I check it on my browser, it says:
Notice: Undefined variable: fnameErr in /opt/lampp/htdocs/eam/add.php on line 81
Notice: Undefined variable: lnameErr in /opt/lampp/htdocs/eam/add.php on line 84
Notice: Undefined variable: emailErr in /opt/lampp/htdocs/eam/add.php on line 89
 
    