How to put a submission limit on a form with PHP - php

Question

I'm trying to create a .php page that contains a form with a submission limit. I'm looking for these steps in order:
User arrives to form
User see's that form is still open
User submits info for form
Form adds +1 to a txt file that will +1 upon every form submission until the txt file reaches the number 10.
If the txt file equals the preset of 10 I would like the form to disappear and allow no more submissions.
I've tried using fopen, and making it work using $limit = fopen("count.txt", "r") but im so confused as to what needs to happen first. The code I'm using are snippets from other php codes I've written and found online. Normally I can figure out things like this as I know its most likely simple.
<?php
$limit = fopen("count.txt", "r") or die("Unable to open file!");
echo fread($myfile,filesize("count.txt"));
if ($limit = 10){
echo ("Cannot Submit Anymore");}
else{
echo ('<form>
First name:<br>
<input type="text" name="firstname"><br>
Last name:<br>
<input type="text" name="lastname">
</form>');}
fclose($myfile);
$limit = fopen('count.txt', 'c+');
flock($limit, LOCK_EX);
$count = (int)fread($limit, filesize('count.txt'));
ftruncate($limit, 0);
fseek($limit, 0);
fwrite($limit, $count + 1);
flock($limit, LOCK_UN);
fclose($limit);
?>
I'm completely stuck and not sure of the order in which everything needs to be to work.

Answer 1

Figured out what I needed to do, although I don't know if the code is compliant. Anyway, here is what I did:
5 Pages Total:
index.php [Landing Page]
tally.php [PHP code for updating the different txt files]
count.txt [How many seats purchased. In this case it had the number 0 typed into it]
left.txt [How many seats left. In this case it had the number 10 typed into it]
max.txt [How many seats im selling. In this case it had the number 10 typed into it]
index.php [Landing Page]:
<?php
$max = file_get_contents('max.txt');
$limit = file_get_contents('count.txt');
$left = file_get_contents('left.txt');
$maxed = 'Sorry, All Seats Have Been Sold';
if ($limit >= $max){
echo $maxed;}
else{
echo '
<form action="tally.php"> // This form can be edited to your needs
First name:<br><input type="text"><br>
Last name:<br><input type="text">
<input type="submit" value="Submit">
</form>' . 'Seats Remaining:' . $left;}
?>
tally.php [PHP code for updating the different txt files]:
<?php
$limit = fopen("count.txt", "c+");
flock($limit, LOCK_EX);
$count = (int)fread($limit, filesize("count.txt"));
ftruncate($limit, 0);
fseek($limit, 0);
fwrite($limit, $count + 1);
flock($limit, LOCK_UN);
fclose($limit);
$left = fopen("left.txt", "c+");
flock($left, LOCK_EX);
$remaining = (int)fread($left, filesize("left.txt"));
ftruncate($left, 0);
fseek($left, 0);
fwrite($left, $remaining - 1);
flock($left, LOCK_UN);
fclose($left);
header('Location: http://www.yoursite.com/'); // this links back to your submission form
exit;
?>
count.txt [How many seats purchased]:
0
left.txt [How many seats left]
10
max.txt [How many seats im selling]
10
Hope this helps someone in the future, this code throws up tons of error logs when ran on my server that I can see in the backend but it works for me and for what I need. If someone can improve upon this one day I and many others in the future would be very grateful.