Prevent WordPress' default input sanitization

Question

Whenever I get an input from a <textarea> or an input filed, WordPress sanitize my input and escape all special characters. How can I disable this feature? For example, if I have the following html code that accept a C++ code such as cout<<"hello world"; WordPress will convert it to cout<<\"hello world\";.

<!--HTML code-->
<form action="/action.php" method="post">
  <input type="text" name="mycode" value="cout<<'hello world';">
  <input type="submit" value="Submit">
</form>

.

<?php
    //PHP code for action.php file
    echo $_POST['mycode'];//This output will have all the special characters escaped
    //I need this to give me the original text entered by the user without /s. 
?>

I am using WordPress version 5.7.2. Any time I use a special characters like \, ', " They will get \ in front of them. I have tried this using different WordPress themes and the result is still the same. If I use stripcslashes($_POST['mycode']) this get ride of these \. But was wondering if there is a way to stop WordPress from doing this from the start. Following shows an image of the input and output I get.

Answer 1

Here's an insanely simple hack-y idea

At the top of /index.php, before WP gets it's greedy little fingers on your incoming data, add this line:

$_SPOST = null;
if (isset($_SERVER['REQUEST_METHOD']) && strtoupper($_SERVER['REQUEST_METHOD']) === 'POST') {
   $_SPOST = $_POST;
}

Then whenever you know you'll be passing code content back to the browser

<?php
    //PHP code for action.php file
    echo $_SPOST['mycode'];//This output will have all the special characters escaped
    //I need this to give me the original text entered by the user without /s. 
?>

But wait, there's more.. we can hook back up within the wordpress ecosystem and transform our post after it's been fiddled with and sanitized.

This page gave me the idea to use parse_request, which fires once all query variables for the current request have been parsed.

function use_spost() {
  if (isset($_SPOST)) $_POST = $_SPOST;
}
add_action('parse_request', 'use_spost', 1);