Convert textarea ready to store in text column with line breaks etc

    $UserNotes = $_POST['UserNotes'];

    $UserNotes = trim($UserNotes);
    $UserNotes = stripslashes($UserNotes);
    $UserNotes = htmlspecialchars($UserNotes, ENT_QUOTES);

\n new line characters will still be stored as \n (htmlspecialchars() doens’t convert them to <br>)

Convert \n character to <br> when displaying

Not needed for a text area (it will respect \n character) but nl2br() is needed when displaying as a general php string:

  $UserNotes = nl2br($UserNotes);