Changes in SAPI modules
Undeprecated features in PHP 5.3.x
Migrating from PHP 5.2.x to PHP 5.3.x
PHP Manual

## Deprecated features in PHP 5.3.x

PHP 5.3.0 introduces two new error levels: `E_DEPRECATED` and `E_USER_DEPRECATED`. The `E_DEPRECATED` error level is used to indicate that a function or feature has been deprecated. The `E_USER_DEPRECATED` level is intended for indicating deprecated features in user code, similarly to the `E_USER_ERROR` and `E_USER_WARNING` levels.

The following is a list of deprecated INI directives. Use of any of these INI directives will cause an `E_DEPRECATED` error to be thrown at startup.

- define_syslog_variables
- register_globals
- register_long_arrays
- safe_mode
- magic_quotes_gpc
- magic_quotes_runtime
- magic_quotes_sybase
- Comments starting with '#' are now deprecated in .INI files.

Deprecated functions:

- call_user_method() (use call_user_func() instead)
- call_user_method_array() (use call_user_func_array() instead)
- define_syslog_variables()
- dl()
- ereg() (use preg_match() instead)
- ereg_replace() (use preg_replace() instead)
- eregi() (use preg_match() with the 'i' modifier instead)
- eregi_replace() (use preg_replace() with the 'i' modifier instead)
- set_magic_quotes_runtime() and its alias, magic_quotes_runtime()
- session_register() (use the $_SESSION superglobal instead)
- session_unregister() (use the $_SESSION superglobal instead)
- session_is_registered() (use the $_SESSION superglobal instead)
- set_socket_blocking() (use stream_set_blocking() instead)
- split() (use preg_split() instead)
- spliti() (use preg_split() with the 'i' modifier instead)
- sql_regcase()
- mysql_db_query() (use mysql_select_db() and mysql_query() instead)
- mysql_escape_string() (use mysql_real_escape_string() instead)
- Passing locale category names as strings is now deprecated. Use the LC_* family of constants instead.
- The `is_dst` parameter to mktime(). Use the new timezone handling functions instead.

Deprecated features:

- Assigning the return value of new by reference is now deprecated.
- Call-time pass-by-reference is now deprecated.
- The use of {} to access string offsets is deprecated. Use [] instead.

Changes in SAPI modules
Undeprecated features in PHP 5.3.x
Migrating from PHP 5.2.x to PHP 5.3.x
PHP Manual