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I have implemented a PHP script.
I run my PHP script via the following URL : http://server/script.php?param1=%80t%80

So I pass a GET parameter to my PHP script.
The parameter is named param1.
param1 contains the string "€t€" which is URL-encoded as "%80t%80".

My PHP script is encoded with the UTF-8 norm.
I was wondering which character encoding applies on the string contained in $_GET["param1"].

For sure the character encoding on $_GET["param1"] is not UTF-8.
The reason : The following command in my PHP script results to "80 74 80" which is the hexadecimal representation of $_GET["param1"].

var_dump(unpack("H*", $_GET["param1"]));

If the character encoding on $_GET["param1"] was UTF-8 then the previous PHP command would result to "e2 82 ac 74 e2 82 ac".

The character encoding on $_GET["param1"] is not ISO-8859-1 neither because the € symbol is not included in the IS0-8859-1 charset.
To view the ISO-8859-1 encoding table go to http://en.wikipedia.org/wiki/ISO/IEC_8859-1
So the PHP internal encoding returned by the mb_internal_encoding function does not apply on $_GET["param1"] because it is IS0-8859-1.

Does anyone know which character encoding applies on the string contained in $_GET["param1"] ?

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I am not sure I understand why you are using unpack while trying to deal with a character-encoding problem you are trying to solve. So here it goes...

I suppose you are trying to read the value of $_GET['param1'] with something like:

$var = $_GET['param1']; I suggest you try urldecode $var = urldecode($_GET['param1']) and then use functions for handling multiByte strings http://gr.php.net/manual/en/ref.mbstring.php or use the iconv functions.

Hope the above helps.

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I have used the unpack function just for a testing purpose. I needed to see the bytes representing the string contained in param1. My final goal is UTF-8 encoding each string received from a GET parameter. I have planned to use the mb_convert_encoding php function but I need to know which encoding is initially used to represent the strings in GET array.
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For sure the character encoding on $_GET["param1"] is not UTF-8. The reason : The following command in my PHP script results to "80 74 80" which is the hexadecimal representation of $_GET["param1"].

This is exactly what you'd expect, because it's what you've written. The parameter %80t%80 means three characters: hex 80, "t", hex 80. %80 means "hex 80". You're manually specify a specific hex value, character encoding doesn't come in to this at all.

Try this:

var_dump( unpack ("H*", urldecode("%80t%80")));

And this:

http://server/script.php?param1=%e2%82%ac%74%e2%82%ac
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According to https://www.w3schools.com/tags/ref_urlencode.ASP:

"URLs can only be sent over the Internet using the ASCII character-set."

Actually a subset of ASCII seems to be what URL-encoding targets. https://www.php.net/manual/en/function.urlencode.php says urlencode():

"is convenient when encoding a string to be used in a query part of a URL, .. to pass variables to the next page... [It] Returns a string in which all non-alphanumeric characters except -_. have been replaced with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs. It is encoded the same way that the posted data from a WWW form is encoded, that is the same way as in application/x-www-form-urlencoded media type. This differs from the » RFC 3986 encoding (see rawurlencode()) in that for historical reasons, spaces are encoded as plus (+) signs."

Those are evidently mappings into alphanumeric ASCII (plus at least ._-+%) from other characters within ASCII or from other character representations within UTF-8 or other charsets. To map back to, say, UTF-8, might require knowing what was started with. Yet in the reverse direction, it is unclear: https://www.php.net/manual/en/function.urldecode.php says that urldecode():

Decodes any %## encoding in the given string. Plus symbols ('+') are decoded to a space character.

Not only it is unclear if the decoding output is UTF-8 or what, but (the reason I found myself looking at this question) when I wanted a '+' to be sent within a parameter via the URL (which arrives into PHP as $_GET["paramName"]), it arrived as a space (' ') as warned above, until I used urlencode($paramVal) to convert '+' to %2B before inserting that into the URL. Then it shows up in the browser's URL widget with ?paramName=...%2B... but arrives in PHP urldecoded as a '+'.

I would hope that the output of PHP urldecode() is UTF-8 since I had among my HTML headers <meta charset="UTF-8">, but that's a guess.

I don't find my answer too helpful to you, but if I could have read my answer to your question, which came up while searching to solve my problem, it would have saved me an hour. Maybe it'll help the next person.

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