Index: typo3/sysext/install/mod/class.tx_install.php
===================================================================
--- typo3/sysext/install/mod/class.tx_install.php	(revision 8269)
+++ typo3/sysext/install/mod/class.tx_install.php	(working copy)
@@ -261,6 +261,12 @@
 		$this->mode = t3lib_div::_GP('mode');
 		if ($this->mode !== '123') {
 			$this->mode = '';
+		} else {
+			$missingPHPModules = $this->getMissingPHPModules();
+			if (count($missingPHPModules) > 0) {
+				t3lib_BEfunc::typo3PrintError('TYPO3 Installation Error', 'The following PHP module(s) is/are missing: ' . implode(', ', $missingPHPModules));
+				die();
+			}
 		}
 		if (t3lib_div::_GP('step') === 'go') {
 			$this->step = 'go';
@@ -4111,6 +4117,21 @@
 		return (is_array($test) ? 1 : 0);
 	}
 
+	/**
+	 * Checks if the essential PHP modules are loaded
+	 *
+	 * @return array list of modules which are missing
+	 */
+	protected function getMissingPHPModules() {
+		$modules = array('filter', 'gd', 'json', 'mysql', 'pcre', 'session', 'SPL', 'standard', 'xml', 'zlib');
+		$result = array();
+		foreach ($modules as $module) {
+			if (!extension_loaded($module)) {
+				$result[] = $module;
+			}
+		}
+		return $result;
+	}
 
 
 
@@ -4120,7 +4141,6 @@
 
 
 
-
 	/*****************************************
 	 *
 	 * ABOUT the isXXX functions.