AJAX POST and Plus Sign ( + ) -- How to Encode?

Question

I'm POSTing the contents of a form field via AJAX to a PHP script and using JavaScript to escape(field_contents). The problem is that any plus signs are being stripped out and replaced by spaces. How can I safely 'encode' the plus sign and then appropriately 'decode' it on the PHP side?

Answer 1

Use encodeURIComponent() in JS and in PHP you should receive the correct values.

Note: When you access $_GET, $_POST or $_REQUEST in PHP, you are retrieving values that have already been decoded.

Example:

In your JS:

// url encode your string
var string = encodeURIComponent('+'); // "%2B"
// send it to your server
window.location = 'http://example.com/?string='+string; // http://example.com/?string=%2B

On your server:

echo $_GET['string']; // "+"

It is only the raw HTTP request that contains the url encoded data.

For a GET request you can retrieve this from the URI. $_SERVER['REQUEST_URI'] or $_SERVER['QUERY_STRING']. For a urlencoded POST, file_get_contents('php://stdin')

NB:

decode() only works for single byte encoded characters. It will not work for the full UTF-8 range.

eg:

text = "\u0100"; // Ā
// incorrect
escape(text); // %u0100 
// correct
encodeURIComponent(text); // "%C4%80"

Note: "%C4%80" is equivalent to: escape('\xc4\x80')

Which is the byte sequence (\xc4\x80) that represents Ā in UTF-8. So if you use encodeURIComponent() your server side must know that it is receiving UTF-8. Otherwise PHP will mangle the encoding.