I have problems to show a var in a text field of the HTML

Hello, I like to ask for help showing a PHP var, coming from a database in an input string with a Value= possibility
Here I show the code that does not work with nicepage:
Woonplaats:
I see the <?php echo $_post;?> in the text field!!

If I use the same code in an extern environment then it works perfectly like:
//Load all the parametrs from the record on the DB
$sql = "SELECT * FROM Persoon WHERE Pin like '$txtPin'";
$result = $mysqli->query($sql);
if ($result->num_rows > 0)

//If the Pin is found, it put on the POST
{
while($row = $result->fetch_assoc()) {
$_POST=$row;
$_POST=$row;
$_POST= $row;
$_POST=$row;
$_POST=$row;
$_POST=$row;
$_POST=$row;
$_POST=$row;
$_POST=$row;
$_POST=$row;
$_POST=$row;

}
}
?>

  Woonplaats: <input type="text" value="<?php echo $_POST['Woonplaats']; ?>"> <br> <br>

This is what I see!
Woonplaats: <?php echo $_post;?>

I do not understand why I see the PHP string in the text field of the input tag!