So, I am trying to understand what is the difference with my string now that it has arrived through a FORM POST instead of a string which i declare in the variable inside my code, when I echo the POST variable it is the correct string. When it reaches Telegram, the new line is no longer interpreted as a new line.

This is part of my code and it works as expected:

$dynamicMessage = "Line One nLineTwo";

// Parameters to be sent in the request
$params = array(
    'chat_id' => $chatId,
    'text' => $dynamicMessage,
    'parse_mode' => 'HTML'
);

Output in my Telegram chat from my Telegram Bot:

Line One
LineTwo

Now, I switch to POST to this and assign to the variable, it does not work as expected:

$dynamicMessage = trim($_POST["updatemessage"]);

// Parameters to be sent in the request
$params = array(
    'chat_id' => $chatId,
    'text' => $dynamicMessage,
    'parse_mode' => 'HTML'
);

Output in my Telegram chat from my Telegram Bot:

Line One nLineTwo