TYPO3 Core

please provide more detailed information or I'm going to close your report otherwise

You can only enter normal parameters for an extension.
E.g.
http://mytypo3domain.com/index.php?id=32&tx_ttextensionname_pi1[param1]=1&tx_ttextensionname_pi1[param2]=2&tx_ttextensionname_pi1[param3]=3

So you have to repeat the rather long extension array for each extension parameter.

It would be shorter to have:

http://mytypo3domain.com/index.php?id=32&tx_ttextensionname_pi1='param1=1&param2=2&param3=3';
This is a proposal in pseudo URL, it must be encoded of course and could be done in better ways. However it would make the URL line smaller and easier to read.
The job to put this into piVars should be done by the tslib_pibase classe.

The relevant code is here:

• Returns the GET/POST global arrays merged with POST taking precedence.
• Usage: 1 *
• @param string Key (variable name) from GET or POST vars
• @return array Returns the GET vars merged recursively onto the POST vars.
• @ignore
• @deprecated
  */
  function GParrayMerged($var) {
  $postA = is_array($_POST[$var]) ? $_POST[$var] : array();
  $getA = is_array($_GET[$var]) ? $_GET[$var] : array();
  $mergedA = t3lib_div::array_merge_recursive_overrule($getA,$postA);
  t3lib_div::stripSlashesOnArray($mergedA);
  return $mergedA;
  }

Argh
After creating a small demo extension I couldn't reproduce the problem. I then noticed that the extension where I found the problem mangled piVars via

if ($this->piVars) {
foreach ($this->piVars as $key => $value)
$this->piVars[$key] = htmlspecialchars(stripslashes($value));
}

and stripslashes destroys the array and "converts" it to the string "Array" :-( (which is documented in the PHP documentation, so it isn't a PHP bug)

Sorry that I didn't notice this mangling earlier. Please close this bug as invalid.

(and: Franz, if you want a better URL parameter scheme, please open a new feature request for it.)

As requested by the reporter, this issue is closed.