Index: tests/t3lib/t3lib_div_testcase.php
===================================================================
--- tests/t3lib/t3lib_div_testcase.php	(revision 7181)
+++ tests/t3lib/t3lib_div_testcase.php	(working copy)
@@ -34,6 +34,28 @@
  */
 class t3lib_div_testcase extends tx_phpunit_testcase {
 	/**
+	 * backup of the global variables _GET, _POST, _SERVER
+	 *
+	 * @var array
+	 */
+	private $backupGlobalVariables;
+
+	public function setUp() {
+		$this->backupGlobalVariables = array(
+			'_GET' => $_GET,
+			'_POST' => $_POST,
+			'_SERVER' => $_SERVER,
+		);
+	}
+
+	public function tearDown() {
+		foreach ($this->backupGlobalVariables as $key => $data) {
+			$GLOBALS[$key] = $data;
+		}
+	}
+
+
+	/**
 	 * @test
 	 */
 	public function checkIntExplodeConvertsStringsToInteger() {
@@ -838,7 +860,7 @@
 	 */
 	public function readLLfileLocallangXMLOverride() {
 		$unique = uniqid('locallangXMLOverrideTest');
-		
+
 		$xml = '<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
 			<T3locallang>
 				<data type="array">
@@ -866,6 +888,155 @@
 
 		unlink($file);
 	}
-}
+
+
+	///////////////////////////////
+	// Tests concerning _GETset()
+	///////////////////////////////
+
+	/**
+	 * @test
+	 */
+	public function getSetCanSetWholeArray() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+		t3lib_div::_GETset(array('oneKey' => 'oneValue'));
+
+		$this->assertEquals(
+			array('oneKey' => 'oneValue'),
+			$_GET
+		);
+		$this->assertEquals(
+			array('oneKey' => 'oneValue'),
+			$GLOBALS['HTTP_GET_VARS']
+		);
+	}
 
+	/**
+	 * @test
+	 */
+	public function getSetForArrayDropsExistingValues() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+
+		t3lib_div::_GETset(array('foo' => 'bar'));
+		t3lib_div::_GETset(array('oneKey' => 'oneValue'));
+
+		$this->assertEquals(
+			array('oneKey' => 'oneValue'),
+			$_GET
+		);
+		$this->assertEquals(
+			array('oneKey' => 'oneValue'),
+			$GLOBALS['HTTP_GET_VARS']
+		);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getSetCanAssignOneValueToOneKey() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+
+		t3lib_div::_GETset('oneValue', 'oneKey');
+
+		$this->assertEquals(
+			'oneValue',
+			$_GET['oneKey']
+		);
+		$this->assertEquals(
+			'oneValue',
+			$GLOBALS['HTTP_GET_VARS']['oneKey']
+		);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getSetForOneValueNotDropsExistingValues() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+
+		t3lib_div::_GETset(array('foo' => 'bar'));
+		t3lib_div::_GETset('oneValue', 'oneKey');
+
+		$this->assertEquals(
+			array('foo' => 'bar', 'oneKey' => 'oneValue'),
+			$_GET
+		);
+		$this->assertEquals(
+			array('foo' => 'bar', 'oneKey' => 'oneValue'),
+			$GLOBALS['HTTP_GET_VARS']
+		);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getCanAssignAnArrayToSpecificArrayElement() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+
+		t3lib_div::_GETset(array('childKey' => 'oneValue'), 'parentKey');
+
+		$this->assertEquals(
+			array('parentKey' => array('childKey' => 'oneValue')),
+			$_GET
+		);
+		$this->assertEquals(
+			array('parentKey' => array('childKey' => 'oneValue')),
+			$GLOBALS['HTTP_GET_VARS']
+		);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getSetCanAssignAValueToSpecificArrayChildElement() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+
+		t3lib_div::_GETset('oneValue', 'parentKey|childKey');
+
+		$this->assertEquals(
+			array('parentKey' => array('childKey' => 'oneValue')),
+			$_GET
+		);
+		$this->assertEquals(
+			array('parentKey' => array('childKey' => 'oneValue')),
+			$GLOBALS['HTTP_GET_VARS']
+		);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getSetCanAssignAnArrayToSpecificArrayChildElement() {
+		$_GET = array();
+		$GLOBALS['HTTP_GET_VARS'] = array();
+
+		t3lib_div::_GETset(
+			array('key1' => 'value1', 'key2' => 'value2'),
+			'parentKey|childKey'
+		);
+
+		$this->assertEquals(
+			array(
+				'parentKey' => array(
+					'childKey' => array('key1' => 'value1', 'key2' => 'value2')
+				)
+			),
+			$_GET
+		);
+		$this->assertEquals(
+			array(
+				'parentKey' => array(
+					'childKey' => array('key1' => 'value1', 'key2' => 'value2')
+				)
+			),
+			$GLOBALS['HTTP_GET_VARS']
+		);
+	}
+}
 ?>
\ No newline at end of file
Index: t3lib/class.t3lib_div.php
===================================================================
--- t3lib/class.t3lib_div.php	(revision 7181)
+++ t3lib/class.t3lib_div.php	(working copy)
@@ -322,25 +322,54 @@
 	}
 
 	/**
-	 * Writes input value to $_GET
+	 * Writes input value to $_GET.
 	 * Usage: 2
 	 *
-	 * @param	mixed		Array to write to $_GET. Values should NOT be escaped at input time (but will be escaped before writing according to TYPO3 standards).
-	 * @param	string		Alternative key; If set, this will not set the WHOLE GET array, but only the key in it specified by this value!
+	 * @param mixed $inputGet
+	 *        array or single value to write to $_GET. Values should NOT be
+	 *        escaped at input time (but will be escaped before writing
+	 *        according to TYPO3 standards).
+	 * @param string $key
+	 *        alternative key; If set, this will not set the WHOLE GET array,
+	 *        but only the key in it specified by this value!
+	 *        You can specify to replace keys on deeper array levels by
+	 *        separating the keys with a pipe.
+	 *        Example: 'parentKey|childKey' will result in
+	 *        array('parentKey' => array('childKey' => $inputGet))
+	 *
 	 * @return	void
 	 */
-	public static function _GETset($inputGet,$key='')	{
-			// ADDS slashes since TYPO3 standard currently is that slashes MUST be applied (regardless of magic_quotes setting).
-		if (strcmp($key,''))	{
-			if (is_array($inputGet)) {
-				self::addSlashesOnArray($inputGet);
+	public static function _GETset($inputGet, $key = '') {
+			// adds slashes since TYPO3 standard currently is that slashes
+			// must be applied (regardless of magic_quotes setting)
+		if (is_array($inputGet)) {
+			self::addSlashesOnArray($inputGet);
+		} else {
+			$inputGet = addslashes($inputGet);
+		}
+
+		if ($key != '') {
+			if (strpos($key, '|') !== FALSE) {
+				$pieces = explode('|', $key);
+				$newGet = array();
+				$pointer =& $newGet;
+				foreach ($pieces as $piece) {
+					$pointer =& $pointer[$piece];
+				}
+				$pointer = $inputGet;
+				$mergedGet = self::array_merge_recursive_overrule(
+					$_GET, $newGet
+				);
+
+				$_GET = $mergedGet;
+				$GLOBALS['HTTP_GET_VARS'] = $mergedGet;
 			} else {
-				$inputGet = addslashes($inputGet);
+				$_GET[$key] = $inputGet;
+				$GLOBALS['HTTP_GET_VARS'][$key] = $inputGet;
 			}
-			$GLOBALS['HTTP_GET_VARS'][$key] = $_GET[$key] = $inputGet;
 		} elseif (is_array($inputGet)) {
-			self::addSlashesOnArray($inputGet);
-			$GLOBALS['HTTP_GET_VARS'] = $_GET = $inputGet;
+			$_GET = $inputGet;
+			$GLOBALS['HTTP_GET_VARS'] = $inputGet;
 		}
 	}