POST'ing multiple comments using file_put_contents - php

Question

Ok, so here is my page (basic template recreated for practice):
http://puu.sh/fRn4b/6d83015087.png
Its all static, bar the form.
What I am attempting to do with said form is to get the contents entered to show up in the little gray box just below (it has overflow set so scroll would be enabled once full).
I started with this:
<form action="index.php" method="post">
<input type="text" name="name" placeholder="Enter your name" required><br>
<textarea name="comment" id="comments" rows="10" required placeholder="Enter your thoughts"></textarea><br>
<input type="submit" name="submit">
</form>
if (isset($_POST['name']) && isset($_POST['comment'])) {
$name = htmlentities($_POST['name']);
$comment = htmlentities($_POST['comment']);
$fullcomment = "<h2>".$name."</h2><p>".$comment."</p>";
echo $fullcomment;
}
That worked, and with the css it looked quite nice. However it would only post one comment and that comment would be lost on reloading. I wanted it to stick. So then the next attempt was:
if (isset($_POST['name']) && isset($_POST['comment'])) {
$file ="./index.php";
$name = htmlentities($_POST['name']);
$comment = htmlentities($_POST['comment']);
$fullcomment = "<h2>".$name."</h2><p>".$comment."</p>";
file_put_contents($file, $fullcomment, FILE_APPEND);
}
Now upon submitting the form, nothing would happen (including no errors). Is it not possible to use file_put_contents on the file said function(?) is in? Because I tried changing the $file to "./index.txt" and that worked, it created a new file and added the forms content within.
As you can probably tell I am extremely new to this. This is me learning. I pick up new things and I think of ways I could apply them, even if said ways are not the most efficient method.
Any help would be great thank-you!
It does work but it adds the content at the end of the document, not within the comment box. Must need to find a different method.
Edit 2: I suppose I could just take the contents from the index.txt troubleshoot and add it to the .php file, but that seems a bit roundabout.
Edit 3: That worked yuhp. Although now refreshing index.php results in repeating the last entered form content, which is rather annoying. Would the solution to that be resetting the variables after the code has run?

Answer 1

You could use Ajax to solve this problem, but if you are not familiar with it, you can try this out :
$file ="./comments.txt";
// When you the page is loaded, get the comments from 'comments.txt'
$fullcomment = file_get_contents($file);
if (isset($_POST['name']) && isset($_POST['comment'])) {
$name = htmlentities($_POST['name']);
$comment = htmlentities($_POST['comment']);
$fullcomment = "<h2>".$name."</h2><p>".$comment."</p>";
file_put_contents($file, $fullcomment, FILE_APPEND);
}