Why is this PHP validation still setting the value - php

Question

I am trying to validate a form field (to be used for First Name) for letters and dashes only, but regardless of how I implement the code, the value of $player_name is still being set.
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (empty($_POST["player_name"])) {
$nameErr = "Name is required";
} else {
$player_name = test_input($_POST["player_name"]);
// check if name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z -]+$/",$player_name)) {
$nameErr = "Only letters and white space allowed";
}
}
}
function test_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
The form has been implemented using the following code:
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
Registration Date: <input type="text" name="date_captured" id="date_captured" value="<?php echo $current_date; ?>">
<br><br>
Name: <input type="text" name="player_name" id="player_name">
<span class="error">* <?php echo $nameErr;?></span>
<br><br>
<input type="submit" name="submit" value="Submit">
</form>
<?php
echo "<h2>Your Input:</h2>";
echo $date_captured;
echo $player_name;
echo "<br>";
?>
Even though the "Only letter and white space allowed" error is set and displayed, the value of $player_name is still set.

Answer 1

I fixed it using the following:
if ($_SERVER["REQUEST_METHOD"] == "POST") {
$fieldTitle = "Player Name";
if (empty($_POST["player_name"])) {
$player_nameErr = $fieldTitle . $requiredErrorText;
} else {
// check if name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z -]*$/",test_input($_POST["player_name"]))) {
$player_nameErr = $nameValidationErrorText;
} else {
$player_name = test_input($_POST["player_name"]);
}
}