else Statement not being triggered after if(empty($var)) - php

Question

I've tried searching for a solution to my problem on stackoverflow but can't seem to find one that fits my situation.
<?php
if (empty($userName)){
print <<<HERE
<form>
Please enter your name:
<input type="text" name="userName">
<br>
<input type="submit">
</form>
HERE;
}
else {
print "<h3>Hi there, $userName!</h3>";
} //end
?>
When I enter a value into the form field it is assigned to the variable $userName but the issue occurs when the else statement is not being triggered after that value has been added.
I hope I've been clear enough, looking forward to a possible solution.
Thank You.

Answer 1

this code only works if register_globals is enabled, and register_global was removed since PHP 5.4.0, so this code won't work in PHP 5.4+, nor will it work if register_globals is disabled in PHP.ini (and it has been disabled-by-default since PHP 4.2.0), try
if (empty($_GET['userName'])){
instead. also, seems you're wide open to XSS here, the variable needs to be escaped before being echoed back to the user, or you open your website to xss attacks by hackers.
try
function hhb_tohtml(string $str):string
{
return htmlentities($str, ENT_QUOTES | ENT_HTML401 | ENT_SUBSTITUTE | ENT_DISALLOWED, 'UTF-8', true);
}
print "<h3>Hi there, ".hhb_tohtml($_GET['userName'])."!</h3>";

Answer 2

How are you retrieving your value from your variable? I don't see that in your question.
<?php
if(isset($_POST['userName'])) {
$userName = $_POST['userName']; //This will take the userName input and put it into a variable for you to test.
}
if (empty($userName)){
print <<<HERE
<form>
Please enter your name:
<input type="text" name="userName">
<br>
<input type="submit">
</form>
HERE;
}
else {
print "<h3>Hi there, $userName!</h3>";
} //end
?>