Sorry, but your problem does not imply a bug in PHP itself.  For a
list of more appropriate places to ask for help using PHP, please
visit http://www.php.net/support.php as this bug system is not the
appropriate forum for asking support questions.  Due to the volume
of reports we can not explain in detail here why your report is not
a bug.  The support channels will be able to provide an explanation
for you.

Thank you for your interest in PHP.

$variable is a string and not an array. 

Your error : "Fatal error: Cannot unset string offsets" is pretty explicit about it. 

You're wrong, var_dump says:

array(1) { ["Try_Login"]=> string(8) "conn_err" } 


It's so an array!

Look: $Query is an array that contains a string at the index "Try_Login". So $Query["Try_Login"] is a string.

You're unsetting $Query["Try_Login"]["Error"] so yes, you're trying to unset an offset of a string.

You're right!

But is this expected to return true?

if (isset($Query["Try_Login"]["Error")) {
  unset($Query["Try_Login"]["Error"]);
}

'Cause that's when I'm trying to unset $Query["Try_Login"]["Error"] ...

Yes this is expected:

non-numeric indexes are interpreted as 0 for string offsets.

so isset($string["foo"]) is equivalent to isset($string[0]) which checks whether the string offset 0 exists, and it does, your string is not empty.

Hey, I don't mean to be annoying, hope didn't get there yet, but check this out:

Query_Repository returns string "conn_err", so it's the same as:
$Query["Try_Login"] = "conn_err";

var_dump( $Query ) results in:
array(1) { ["Try_Login"]=> string(8) "conn_err" }

There's no suck key as ["Error"] at all ...

So what you mean is that isset will recognize $Query["Try_Login"]["Error"] as $Query["Try_Login"][0] because of the string offset and then return true?

You may be right, that may be in fact the current behavior, but I don't see how that can be the best behavior at all! 

I'm no expert though. So thank you very much for taking the time to reply. I do appreciate it.

for the last time, you've $Query['Try_Login'] = "conn_err"; and you're doing an isset($Query['Try_Login']['Error']);

So, $Query['Try_Login'] is a string.

This is equivalent to $mystring = "conn_err"; and isset($mystring['Error']) which is equivalent to isset($mystring[0]);

You're wrongly using isset() here, You probably want to check whether 'Error' is a defined index of $Query, so do isset($Query['Error']).. instead of isset($Query['Try_Login']['Error']).

But really bugs.php.net is not a place for that kind of support, you should check out php.net/support and find a medium that suits you better.

Regards.