Undefined array key "HTTP_ACCEPT_CHARSET" PHP8

[ohno]

Slowly working through errors when trying PHP 8, I'm getting Undefined array key "HTTP_ACCEPT_CHARSET", the code snippet in question : -

 

function CreateSignature()
	{
		$sig = @$_SERVER["HTTP_USER_AGENT"].@$_SERVER["HTTP_ACCEPT"].@$_SERVER["HTTP_ACCEPT_LANGUAGE"].@$_SERVER["HTTP_ACCEPT_CHARSET"];
		$this->Signature = md5(Communication::GetIP() . $sig);
	}

I'm guessing the @ is the issue but how to fix?

[maxxd]

@ will suppress errors/notifications. The problem you're running in to is that $_SERVER['HTTP_ACCEPT_CHARSET'] isn't set and therefor can't be used; you're seeing the error despite the @ operator because it won't suppress fatal errors. Your best bet is to use isset() to check each $_SERVER array key and then only use the ones that exist to build the key.

[ohno]

Thanks, that's what I thought but unsure how to code it?

[ginerjm]

if (isset($_SERVER['HTTP_ACCEPT_CHARSET']))

   

[Barand]

1 hour ago, maxxd said:

you're seeing the error despite the @ operator because it won't suppress fatal errors

But it isn't a fatal error, just a warning.

    echo "Version " . phpversion() . '<br><br>';
    
    $keys = ['HTTP_USER_AGENT', 'HTTP_ACCEPT', 'HTTP_ACCEPT_LANGUAGE', 'HTTP_ACCEPT_CHARSET'];

    foreach ($keys as $k) {
        echo "<b>$k</b>
              <br>
              {$_SERVER[$k]}
              <br><br>";
    }

Outputs ...

Further, using the "@" suppresses the warning as expected when I run the OP's code

PS An alternative to using the "@" could be

 $keys = ['HTTP_USER_AGENT', 'HTTP_ACCEPT', 'HTTP_ACCEPT_LANGUAGE', 'HTTP_ACCEPT_CHARSET'];
    $sig = '';
    foreach ($keys as $k) {
        $sig .= $_SERVER[$k] ?? '';
    }

 

[ohno]

The programs error log gives me this : - 24.01.23 13:48:36 31.111.2.99 ERR# 2 Undefined array key "HTTP_ACCEPT_CHARSET" /home/website/public_html/online-support/_lib/objects.global.users.inc.php IN LINE 2175

 

Using your code example: -

Version 7.4.33

HTTP_USER_AGENT
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/109.0

HTTP_ACCEPT
text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8

HTTP_ACCEPT_LANGUAGE
en-GB,en;q=0.5

HTTP_ACCEPT_CHARSET

 

Version 8.0.26

HTTP_USER_AGENT
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:109.0) Gecko/20100101 Firefox/109.0

HTTP_ACCEPT
text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8

HTTP_ACCEPT_LANGUAGE
en-GB,en;q=0.5


Warning: Undefined array key "HTTP_ACCEPT_CHARSET"
HTTP_ACCEPT_CHARSET

 

I don't seem to be able to suppress the error with @?

[Barand]

Did you try the alternative that I added?

[ohno]

I did but I still get : -

Warning: Undefined array key "HTTP_ACCEPT_CHARSET" in /home/website/public_html/test.php on line 12
HTTP_ACCEPT_CHARSET

 

[ohno]

OK, changing the original file to this : -

function CreateSignature()
	{
		$keys = ['HTTP_USER_AGENT', 'HTTP_ACCEPT', 'HTTP_ACCEPT_LANGUAGE', 'HTTP_ACCEPT_CHARSET'];
		$sig = '';
		foreach ($keys as $k) {
        $sig .= $_SERVER[$k] ?? '';
    }
		//$sig = @$_SERVER["HTTP_USER_AGENT"].@$_SERVER["HTTP_ACCEPT"].@$_SERVER["HTTP_ACCEPT_LANGUAGE"].@$_SERVER["HTTP_ACCEPT_CHARSET"];
		$this->Signature = md5(Communication::GetIP() . $sig);
	}

Cleared that error, now the programs logs have this error : -

24.01.23 15:00:38 31.111.2.99 ERR# 2 Undefined array key "p_gl_t" /home/website/public_html/online-support/_lib/objects.internal.inc.php IN LINE 303

 

Line 303 : -

if(($hash = substr(md5(Server::$Response->Typing),0,5)) != @$_POST["p_gl_t"] && strlen(Server::$Response->Typing) > 0)

😪

[Barand]

Have you checked the content of the $_POST array?

Have you checked if any data been posted to that page?

[ginerjm]

You really should stop using the @ sign in any php code.  No sense in it.  If there is an error to be hidden it is better to program to handle it than ignore (hide) it.

[maxxd]

13 hours ago, Barand said:

But it isn't a fatal error, just a warning.

Huh. I could've sworn I read somewhere that non-existent array indexes were promoted to fatal errors - I must be mistaken.

[ohno]

15 hours ago, ginerjm said:

You really should stop using the @ sign in any php code.  No sense in it.  If there is an error to be hidden it is better to program to handle it than ignore (hide) it.

This isn't my code, it's a third party chat system which I'm trying to get to work with PHP 8. I ALWAYS try & fix errors hence this thread!

[ohno]

15 hours ago, Barand said:

Have you checked the content of the $_POST array?

Have you checked if any data been posted to that page?

Not sure how I can check this? The error appears if a webpage with the chat icon is accessed/refreshed.

[ohno]

How does this look?

 

$hash = substr(md5(Server::$Response->Typing),0,5);
if (!is_null($hash) && isset($_POST["p_gl_t"]) && $hash != $_POST["p_gl_t"] && strlen(Server::$Response->Typing) > 0) {
    Server::$Response->XML .= "<gl_typ h=\"".base64_encode($hash)."\">\r\n" . Server::$Response->Typing . "</gl_typ>\r\n";
}

 

[benanamen]

The @ symbol in front of the variables in this code is called an error suppression operator. It is used to suppress error messages that would be generated when trying to access an undefined array key. However, this can make it difficult to identify and fix errors in your code.

Instead of using the error suppression operator, you can check if the key exists in the array before trying to access it. You can use the isset() function to check if a variable is set, and the array_key_exists() function to check if a key exists in an array.

Here is an example of how you can update the code to check for the existence of the key before accessing it:

function CreateSignature()
{
    $sig = "";
    if (isset($_SERVER["HTTP_USER_AGENT"])) {
        $sig .= $_SERVER["HTTP_USER_AGENT"];
    }
    if (isset($_SERVER["HTTP_ACCEPT"])) {
        $sig .= $_SERVER["HTTP_ACCEPT"];
    }
    if (isset($_SERVER["HTTP_ACCEPT_LANGUAGE"])) {
        $sig .= $_SERVER["HTTP_ACCEPT_LANGUAGE"];
    }
    if (isset($_SERVER["HTTP_ACCEPT_CHARSET"])) {
        $sig .= $_SERVER["HTTP_ACCEPT_CHARSET"];
    }
    $this->Signature = md5(Communication::GetIP() . $sig);
}

You can also use the ternary operator to shorten the code

function CreateSignature()
{
    $sig = isset($_SERVER["HTTP_USER_AGENT"]) ? $_SERVER["HTTP_USER_AGENT"] : "";
    $sig .= isset($_SERVER["HTTP_ACCEPT"]) ? $_SERVER["HTTP_ACCEPT"] : "";
    $sig .= isset($_SERVER["HTTP_ACCEPT_LANGUAGE"]) ? $_SERVER["HTTP_ACCEPT_LANGUAGE"] : "";
    $sig .= isset($_SERVER["HTTP_ACCEPT_CHARSET"]) ? $_SERVER["HTTP_ACCEPT_CHARSET"] : "";
    $this->Signature = md5(Communication::GetIP() . $sig);
}