This is the second LTS (long term support) release of TYPO3 CMS.The new release focuses on stability and modernization.

Here we are listing some major changes from 4.5 –

*  Fluid based template.

*  The File Abstraction Layer (FAL) was introduced with TYPO3 6.0 for managing media files regardless of where they are stored in locally or in the cloud.
Each time when the selected, it’s data comes along with file, so the editors can keep track of images and update them from a single location.

*  This version supports rendering responsive image in the front-end.

*  It provides a complete custom rendering mode user will get a full control on rendering.

*  Now the back-end is more smooth and less distracted.

*  In this version the back-end layout can also be stored in files.

*  New improvements are added to make the template more flexible.

*  File Abstraction Layer with typo script improved a lot so File metadata are accessible through registers in file links, FILES cObject also improved.

*  For session date now it only sets a front-end user cookie so it optimizes the reverse proxies and minimizes traffic.

*  new feature Clear all caches, Check for broken Extensions, Core Updater are added in install tool.

*  Caching Groups: cache menu modified and now it has only two options.”Flush general caches” which removes front-end caches and extension specific caches. “Flush front-end caches”, which clears all page related caches.

*  Package Management : It helps work together with PHP libraries and TYPO3 Flow packages to the TYPO3 CMS eco-system.

*  Through mysqli and the TYPO3_DB API support prepared statements.

*  Security : Added salted-password in Install Tool and all back-end users.

Issues we faced when upgrading extensions in typo 3 4.5 to typo 3 6.2 :

Mainly we faced issues regarding mysql statements and here i am explains the changes done.

*  mysql(TYPO3_db, ‘Query string’) did not works for typo3 6.2, replaced this function with $GLOBALS[‘TYPO3_DB’]-                                                                                                                        >exec_SELECTquery($select_fields,$from_table,$where_clause,$groupBy,$orderBy,$limit);

*  ‘mysql_query()’ did not works for typo3 6.2, replaced this function with $GLOBALS[‘TYPO3_DB’]-                                                                                                                                                         >exec_INSERTquery(‘from_table_name’,array(‘feild_name_1’=>’values_1′,’feild_name_2’=>’values_2’));

*  ‘mysql_insert_id()’ did not works for typo3 6.2, replaced this function with $GLOBALS[‘TYPO3_DB’]->sql_insert_id();

*  ‘mysql_fetch_array()’ did not works for typo3 6.2, replaced this function with $GLOBALS[‘TYPO3_DB’]->sql_fetch_assoc();

We successfully updated our catalog extension support from 4.5 to 6.2 by above fixes.
http://www.typo3.org/extensions/repository/view/titech_catalog