detect Linebreaks, Tabs and other special characters inputed by the user with php

Question

I have some functions where I need some parameters given by the user.

The parameters are mostly characters. The Problem I have is, in PHP it is pretty easy to create linebreak- and tab-characters by typing "\n" and "\t".

I want the user to be able to make the same input. (typing "\n" for linebreaks ...)

The problem I am having is, that if I have a code like this:

$character1 = "\n";
$character2 = $_POST["line_break"]; // the user input is "\n"

var_dump($character1);
var_dump($character2);

The output will look like this:

string(1) "
"
string(2) "\n"

The first one is the one I want.

The only solution I could think of is checking the character for all possible inputs and replace it like this:

if ($character2 == "\\n") $character2 = "\n";
elseif ($character2 == "\\t") $character2 = "\t";
elseif ...

This seems like a pretty dirty solution. Is there any other, easyer or cleaner method to achive the result I want?

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The solution can be a JavaScript solution as well if its the only way, because the user interface will work with Ajax request anyway.

Answer 1

You can use eval function of PHP with care:

$character2 = eval('return "' . $_REQUEST["line_break"] . '";');

Note that since we are returning quoted value taken from $_REQUEST["line_break"] some obvious risks of using eval can be avoided.