Test if string is URL encoded in PHP

Question

How can I test if a string is URL encoded?

Which of the following approaches is better?

• Search the string for characters which would be encoded, which aren't, and if any exist then its not encoded, or
• Use something like this which I've made:

function is_urlEncoded($string){
 $test_string = $string;
 while(urldecode($test_string) != $test_string){
  $test_string = urldecode($test_string);
 }
 return (urlencode($test_string) == $string)?True:False; 
}

$t = "Hello World > how are you?";
if(is_urlEncoded($sreq)){
 print "Was Encoded.\n";
}else{
 print "Not Encoded.\n";
 print "Should be ".urlencode($sreq)."\n";
}

The above code works, but not in instances where the string has been doubly encoded, as in these examples:

• $t = "Hello%2BWorld%2B%253E%2Bhow%2Bare%2Byou%253F";
• $t = "Hello+World%2B%253E%2Bhow%2Bare%2Byou%253F";

Answer 1

You'll never know for sure if a string is URL-encoded or if it was supposed to have the sequence %2B in it. Instead, it probably depends on where the string came from, i.e. if it was hand-crafted or from some application.

Is it better to search the string for characters which would be encoded, which aren't, and if any exist then its not encoded.

I think this is a better approach, since it would take care of things that have been done programmatically (assuming the application would not have left a non-encoded character behind).

One thing that will be confusing here... Technically, the % "should be" encoded if it will be present in the final value, since it is a special character. You might have to combine your approaches to look for should-be-encoded characters as well as validating that the string decodes successfully if none are found.

Answer 2

i have one trick :

you can do this to prevent doubly encode. Every time first decode then again encode;

$string = urldecode($string);

Then do again

$string = urlencode($string);

Performing this way we can avoid double encode :)

Answer 3

Here is something i just put together.

if ( urlencode(urldecode($data)) === $data){
    echo 'string urlencoded';
} else {
    echo 'string is NOT urlencoded';
}

Answer 4

I think there's no foolproof way to do it. For example, consider the following:

$t = "A+B";

Is that an URL encoded "A B" or does it need to be encoded to "A%2BB"?

Answer 5

well, the term "url encoded" is a bit vague, perhaps simple regex check will do the trick

$is_encoded = preg_match('~%[0-9A-F]{2}~i', $string);

Answer 6

There's no reliable way to do this, as there are strings which stay the same through the encoding process, i.e. is "abc" encoded or not? There's no clear answer. Also, as you've encountered, some characters have multiple encodings... But...

Your decode-check-encode-check scheme fails due to the fact that some characters may be encoded in more than one way. However, a slight modification to your function should be fairly reliable, just check if the decode modifies the string, if it does, it was encoded.

It won't be fool proof of course, as "10+20=30" will return true (+ gets converted to space), but we're actually just doing arithmetic. I suppose this is what you're scheme is attempting to counter, I'm sorry to say that I don't think there's a perfect solution.

HTH.

Edit:
As I entioned in my own comment (just reiterating here for clarity), a good compromise would probably be to check for invalid characters in your url (e.g. space), and if there are some it's not encoded. If there are none, try to decode and see if the string changes. This still won't handle the arithmetic above (which is impossible), but it'll hopefully be sufficient.

Answer 7

What about:

if (urldecode(trim($url)) == trim($url)) { $url_form = 'decoded'; }
  else { $url_form = 'encoded'; }

Will not work with double encoding but this is out of scope anyway I suppose?

Answer 8

@user187291 code works and only fails when + is not encoded.

I know this is very old post. But this worked to me.

$is_encoded = preg_match('~%[0-9A-F]{2}~i', $string);
if($is_encoded) {
 $string  = urlencode(urldecode(str_replace(['+','='], ['%2B','%3D'], $string)));
} else {
  $string = urlencode($string);
}

Answer 9

send a variable that flags the decode when you already getting data from an url.

?path=folder/new%20file.txt&decode=1

Answer 10

I am using the following test to see if strings have been urlencoded:

if(urlencode($str) != str_replace(['%','+'], ['%25','%2B'], $str))

If a string has already been urlencoded, the only characters that will changed by double encoding are % (which starts all encoded character strings) and + (which replaces spaces.) Change them back and you should have the original string.

Let me know if this works for you.

Answer 11

I found.
The url is For Exapmle: https://example.com/xD?foo=bar&uri=https%3A%2F%2Fexample.com%2FxD
You need Found $_GET['uri'] is encoded or not:

preg_match("/.*uri=(.*)&?.*/", $_SERVER['REQUEST_URI'], $r);
if (isset($_GET['uri']) && urldecode($r['1']) === $r['1']) {
  // Code Here if url is not encoded
}

Answer 12

private static boolean isEncodedText(String val, String... encoding) throws UnsupportedEncodingException { String decodedText = URLDecoder.decode(val, TransformFetchConstants.DEFAULT_CHARSET);

    if(encoding != null && encoding.length > 0){
        decodedText = URLDecoder.decode(val, encoding[0]);
    }

    String encodedText =  URLEncoder.encode(decodedText);

    return encodedText.equalsIgnoreCase(val) || !decodedText.equalsIgnoreCase(val);

}