Using PHP's urldecode() Function: Concepts, Syntax, and Examples

When developing web applications, it is often necessary to encode and decode URLs; PHP provides built‑in functions for this purpose, one of which is urldecode() .

URL encoding replaces characters that are not allowed in URLs (such as spaces, slashes, and question marks) with a percent‑encoded representation, while URL decoding restores the original characters.

The urldecode() function decodes a URL‑encoded string. It accepts a single string argument and returns the decoded original string.

string urldecode ( string $str )

The function only takes one parameter—the string to be decoded—and returns the decoded result.

Below is an example. First, a parameter is encoded using urlencode() :

$param = "hello world";
$urlParam = urlencode($param);

The resulting $urlParam contains the value "hello%20world". This encoded value is then decoded with urldecode() :

$decodedParam = urldecode($urlParam);
echo $decodedParam;

Running the code outputs "hello world", demonstrating that urldecode() successfully converts the encoded URL parameter back to its original form.

Note that urldecode() cannot properly decode non‑printable characters in the range %00‑%20 or non‑ASCII characters below %7F. For such cases, the rawurldecode() function should be used.

In summary, urldecode() is a useful PHP function for decoding URL‑encoded strings, enabling developers to easily revert encoded data to its original representation.