Php "How to remove an instruction after submitting" - php

Question

my code does work properly I am just having trouble with removing "Please enter your name" and only displaying the welcome message after the user submits their name.
I've tried to use conditional statements that just led to an error
<?php
# filter input
function filter($var) {
return htmlspecialchars(stripslashes(trim($var)));
}# validate name
function validate_name(&$name, &$err){
if(empty($name)){
$err = "Name is required";
return;
}
$name = filter($name);
if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
$err = "Only letters and white space allowed";
}
}//$method = filter_input(INPUT_SERVER, 'REQUEST_METHOD');
$method = $_SERVER["REQUEST_METHOD"];
$err = "";
# If client post a name, then validate the name
if ($method === "POST"){
$name = isset($_POST["name"])? $_POST["name"]: "";
validate_name($name, $err);
}
?>
<!-- The form -->
<form method="post">
<center><label>
<input type="text" name="name" value="<?php echo #$name;?>">
</label></center>
<!-- Show if no error -->
<?php if(empty($err)) { ?>
<span><p class="centered-text">Please enter your name</span>
<?php } else { ?>
<!-- Show if error -->
<span class="error">
<?php echo $err ?>
</span>
<?php } ?>
<br>
<input type="submit" name="submit" value="Submit">
</form>
<?php if(isset($name) && empty($err)){ ?>
<p class=" centered-text">Hi <?php echo $name?>!</p>
<p class="centered-text">Welcome to our store!</p>
<?php } ?>
My expected result is to display "please enter your name" and once the user submits to remove the instruction "please enter your name" and display the welcome message only

Answer 1

<?php
# filter input
function filter($var) {
return htmlspecialchars(stripslashes(trim($var)));
}
# validate name
function validate_name(&$name, &$err){
if(empty($name)){
$err = "Name is required";
return;
}
$name = filter($name);
if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
$err = "Only letters and white space allowed";
}
}//$method = filter_input(INPUT_SERVER, 'REQUEST_METHOD');
$method = $_SERVER["REQUEST_METHOD"];
$err = "";
# If client post a name, then validate the name
if ($method === "POST"){
$name = isset($_POST["name"])? $_POST["name"]: "";
validate_name($name, $err);
}
if(isset($name) && empty($err)){ ?>
<p class=" centered-text">Hi <?php echo $name?>!</p>
<p class="centered-text">Welcome to our store!</p>
<?php } else { ?>
<!-- The form -->
<form method="post">
<center><label>
<input type="text" name="name" value="<?php echo #$name;?>">
</label></center>
<!-- Show if no error -->
<?php if(empty($err)) { ?>
<span><p class="centered-text">Please enter your name</span>
<?php } else { ?>
<!-- Show if error -->
<span class="error">
<?php echo $err ?>
</span>
<?php } ?>
<br>
<input type="submit" name="submit" value="Submit">
</form>
<?php } ?>

Answer 2

The error check should only be done if $name is set. If it's not set, the form hasn't been submitted and you should only show the "Please enter your name" message in that case.
Here's the basic logic (HTML not included to improve clarity):
if (!isset($name)) {
// Name has not been submitted yet, show "Please enter your name" message
else {
if (empty($err)) {
// Name was submitted and validated successfully, show welcome message
} else {
// Name was submitted with errors, show the errors
}
}