How can I require a captcha to load a page? - php

Question

I would like a simple PHP captcha script that would require the user so solve a captcha to load the website page. Preferably a captcha that doesn't need a third party such as reCAPTCHA, all done locally.
EDIT: Ended up making a text box to enter the link you would like to protect and it would automatically generate a captcha protected link, and a deletion link to delete the protected link.

Answer 1

You can look at the example here:
https://code.tutsplus.com/tutorials/build-your-own-captcha-and-contact-form-in-php--net-5362
I would also recommend using the timer on your page since bots are becoming better at passing capchas. By timer, I mean time between landing on the page and creating an account/submitting the form.

Answer 2

This is VERY simple. Usually no one is going to put any effort to bypass the captcha unless you have something worth while aka $$$$.
Just post an image with a question. Like What is 345 x 100,000 + 957?
The have an small form with a <input> for them to answer.
You could have any number of images and answers.
$captcha[] = array($answer,$image);
$captcha[] = array($answer,$image);
$captcha[] = array($answer,$image);
Then
$cnt = count($captcha) - 1;
$rec = rand(0,$cnt);
$answer= captcha[$rec][0];
$image = captcha[$rec][1];
echo '<img scr="$image"/>';
echo '<form action="$url" method="post">';
echo '<input type = "text" name="answer" /></form>';
$id = intval(str_replace('.','',$_SERVER['REMOTE_ADDR']));
file_put_contents("$id.txt",$answer);
The in the $url page:
$id = intval(str_replace('.','',$_SERVER['REMOTE_ADDR']));
$answer = intval(file_get_contents("$id.txt"));
unlink("$id.txt");
$pass = false;
if $answer == intval($_POST['answer']){$pass = true;}