What is URLencode and URLdecode?

Definition 1:
urlencode() returns the URL encoded version of the given string.
URL coding converts special characters into % signs followed by two hex digits.

For example: urlencode("10.00%") will return "10%2E00%25".
URL encoded strings are safe to be used as part of URLs.
urldecode() returns the URL decoded version of the given string.

Definition 2:
string urlencode(str) - Returns the URL encoded version of the input string.
String values to be used in URL query string need to be URL encoded.

In the URL encoded version:
Alphanumeric characters are maintained as is.
Space characters are converted to "+" characters.
Other non-alphanumeric characters are converted "%" followed by two hex digits representing the converted character.

string urldecode(str) - Returns the original string of the input URL encoded string.

For example:

$discount ="10.00%";
$url = "http://domain.com/submit.php?disc=".urlencode($discount);
echo $url;

You will get "http://domain.com/submit.php?disc=10%2E00%25".

URL encoder will make youe wen\bsite more secure which in term, improves your website quality.