Untitled

<?php
$errorUsername = "";
$sendUsername = "";
$userame = "";
$errorEmail = "";
$sendEmail = "";
$userEmail = "";
$userPassword = "";
$confirmPassword = "";
$errorPassword = "";

$errors = [
    "emptyName"             => "The field username is required!",
    "biggerSmallerName"     => "The username should be bigger than 4 characters and smaller than 9!",
    "onlyAlphaNumb"         => "The username should content only aphabet and numbers!",
    "validateEmail"         => "The e-mail is required! Please, enter a valid email format!",
    "emptyPassword"         => "The field password is required!",
    "biggerSmallerPassword" => "The password should be bigger than 4 characters and smaller than 9!",
    "numbAlphaPassword"     => "Password must include at least one number!",
    "alphaNumbPassword"     => "Password must include at least one letter!",
    "confirmPassword"       => "Please make sure your passwords match."
];
function validateData ($data) {
    $data = trim($data);
    $data = stripcslashes($data);
    $data = htmlspecialchars($data);
    $data = strtolower($data);
    return $data;
}
//USERNAME VALIDATION
if ($_SERVER ["REQUEST_METHOD"] == "POST") {
    if (empty($_POST ["username"])){
        $errorUsername = $errors["emptyName"];
    }
    elseif (mb_strlen ($_POST ["username"]) <4 || (mb_strlen ($_POST ["username"]) > 9 )) {
        $errorUsername = $errors["biggerSmallerName"];
    }
    elseif (!preg_match('/^[a-zA-Z0-9]+$/', $_POST ["username"])) {
        $errorUsername = $errors["onlyAlphaNumb"];
    }
    else {
        $sendUsername = validateData($_POST ["username"]);
    }
}
//MAIL VALIDATION
if ($_SERVER ["REQUEST_METHOD"] == "POST") {
    if (!filter_var(($_POST ["useremail"]), FILTER_VALIDATE_EMAIL)){
        $errorEmail = $errors["validateEmail"];
    }
    else {
        $sendEmail = validateData($_POST ["useremail"]);
    }
}

//PASSWORD VALIDATION
if ($_SERVER ["REQUEST_METHOD"] == "POST") {
    if (empty($_POST ["password"])){
        $errorPassword = $errors["emptyPassword"];
    }
    elseif (mb_strlen ($_POST ["password"]) <4 || (mb_strlen ($_POST ["password"]) > 9 )) {
        $errorPassword = $errors["biggerSmallerPassword"];
    }
    elseif (!preg_match(("#[0-9]+#"), $_POST ["password"])) {
        $errorPassword = $errors["numbAlphaPassword"];
    }
    elseif (!preg_match(("#[a-z]+#"), $_POST ["password"])) {
        $errorPassword = $errors["alphaNumbPassword"];
    }
    elseif ($_POST ["password"] !== $_POST ["confirmPassword"]) {
        $errorPassword = $errors["confirmPassword"];
    }
    else {
        $sendUsername = validateData($_POST ["password"]);
    }
}


?>
<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>
        Form Validation
    </title>
</head>
<body>
<form action="
<?php echo htmlspecialchars($_SERVER ["PHP_SELF"]); ?>" method="POST">
    <div>
        <label for="username">Please, enter an username:</label>
        <br>
        <input type="text" name="username" id="username">
        <span><?php echo $errorUsername;?></span>
    </div>
    <div>
        <label for="useremail">Please, enter an e-mail:</label>
        <br>
        <input type="email" name="useremail" id="useremail">
        <span><?php echo $errorEmail;?></span>
    </div>
    <div>
        <label for="password">Please, enter a password:</label>
        <br>
        <input type="password" name="password" id="password">
        <span><?php echo $errorPassword;?></span>
    </div>
    <div>
        <label for="confirmPassword">Please, confirm your password:</label>
        <br>
        <input type="password" name="confirmPassword" id="password">
    </div>
    <div>
        <input type="reset" value="Reset">
        <input type="submit" value="Submit">
    </div>
</form>
</body>
</html>