How to Use PHP's urldecode() Function for URL Decoding

In web application development, handling URL encoding and decoding is common, and PHP provides built‑in functions for this purpose, such as urldecode() .

URL encoding replaces characters that are not allowed in a URL (e.g., spaces, slashes, 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 result. Its prototype is:

string urldecode ( string $str )

The function takes one parameter—the encoded string—and returns the original string after decoding.

Below is an example that first encodes a parameter using urlencode() and then decodes it with urldecode() :

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

The variable $urlParam now holds the value hello%20world . Decoding it:

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

Running the code outputs hello world , demonstrating that urldecode() successfully converts the encoded 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 retrieve original data from encoded parameters.