Index: t3lib/class.t3lib_extmgm.php
===================================================================
--- t3lib/class.t3lib_extmgm.php	(revision 7453)
+++ t3lib/class.t3lib_extmgm.php	(working copy)
@@ -122,6 +122,24 @@
 	 ***************************************/
 
 	/**
+	 * Returns true if the extension with extension key $key is installed.
+	 *
+	 * @param	string		Extension key to test
+	 * @param	boolean		If $exitOnError is true and the extension is not loaded the function will die with an error message
+	 * @return	boolean
+	 */
+	public static function isInstalled($key, $exitOnError=0) {
+		$isInstalled = t3lib_div::inList($GLOBALS['TYPO3_CONF_VARS']['EXT']['extList'], $key);
+		if ($exitOnError && !isset($isInstalled)) {
+			throw new BadFunctionCallException(
+				'TYPO3 Fatal Error: Extension "' . $key . '" was not installed!',
+				1272625953
+			);
+		}
+		return $isInstalled;
+	}
+
+	/**
 	 * Returns true if the extension with extension key $key is loaded.
 	 * Usage: 109
 	 *