Question in Homework Help Novelguide: Help coding PHP in Notepad++?

So I'm attempting to practice PHP and entered the following code into Notepad ++:

<?php
echo "<h1>Car Science</h1>";
?>

After doing this I saved the file as one.php and clicked run in Firefox. It did as expect and gave me an H1 heading but it also had this behind it:

"; ?>

Is there a way to fix this problem or will i need a different program altogether? Please respond with bullet list instructions that are clear and concise, it will be greatly appreciated.