Changes to INI file handling
Migrating from PHP 5.2.x to PHP 5.3.x
Migrating from PHP 5.3.x to PHP 5.4.x
PHP Manual

## Other changes

- The default character set for htmlspecialchars() and htmlentities() is now UTF-8, instead of ISO-8859-1. Note that changing your output charset via the default_charset configuration setting does not affect htmlspecialchars/htmlentities unless you are passing "" (an empty string) as the encoding parameter to your htmlspecialchars()/ htmlentities() calls. Generally we do not recommend doing this because you should be able to change your output charset without affecting the runtime charset used by these functions. The safest approach is to explicitly set the charset on each call to htmlspecialchars() and htmlentities().
- `E_ALL` now includes `E_STRICT` level errors in the error_reporting configuration directive.
- SNMP now has an OOP API. Functions now return `FALSE` on every error condition including SNMP-related (no such instance, end of MIB, etc). Thus, in particular, breaks previous behavior of get/walk functions returning an empty string on SNMP-related errors. Multi OID get/getnext/set queries are now supported. Dropped UCD-SNMP compatibility code, consider upgrading to net-snmp v5.3+, Net-SNMP v5.4+ is required for Windows version. In sake of adding support for IPv6 DNS name resolution of remote SNMP agent (peer) is done by extension now, not by Net-SNMP library anymore.
- OpenSSL now supports AES.
- CLI SAPI doesn't terminate any more on fatal errors when using interactive mode with readline support.
- $_SERVER['REQUEST_TIME_FLOAT'] has been added to include microsecond precision.
- Added new hash algorithms: fnv132, fnv164, joaat
- Chained string offsets - e.g. $a[0][0] where $a is a string - now work.
- Arrays cast from SimpleXMLElement now always contain all nodes instead of just the first matching node. All SimpleXMLElement children are now always printed when using var_dump(), var_export() and print_r().
- It's now possible to enforce the class' __construct arguments in an abstract constructor in the base class.

Changes to INI file handling
Migrating from PHP 5.2.x to PHP 5.3.x
Migrating from PHP 5.3.x to PHP 5.4.x
PHP Manual