O lista cu modificarile care apar in PHP6 a fost pregatita de http://blog.tuvinh.com/one-minute-with-php6/.

1. FILE_BINARY and FILE_TEXT constants available for use with filesystem functions.
2. register_globals will be gone.
3. magic_quotes will also disappear.
4. $HTTP_*_VARS has been removed, in favour for $_GET, $_POST, etc.
5. ereg() no longer available in core PHP6.
6. Initiating objects with the reference operator (& new Object()) will generate E_STRICT error.
7. E_STRICT error messages are included in E_ALL errors.
8. {} for string offsets no longer available.
9. [] un-deprecated for accessing characters in a string.
10. ASP-style tags can no longer be used.
11. Better Unicode Support.
12. var will be an alias of public, and raises E_STRICT warning.
13. Support for 64 bit integers.
14. With ternary operator, the “true” expression is no longer required – this can be done: $a = $s ?: ‘b’; (Not clear yet exactly how this will work).
15. zend.ze1_compatibility_mode removed.
16. safe_mode is being removed.
17. Freetype1 and GD1 support removed.
18. dl() is only enabled when a SAPI layers registers it explicitly.
19. Support for dynamic break levels removed.
20. XMLReader and XMLWriter will be in the core distribution.
21. mime_magic removed from the core.
22. Fileinfo moved to the core.
23. ext/soap on by default.
24. foreach supports multi-dimensional arrays: foreach($a as $b => list($c, $d))
25. microtime() will return as float by default.
26. opcode cache included in core distribution, but turned off by default.
27. flags parameter available for file_get_contents().
28. before_needle parameter added to strstr() – allows strstr() to return part of haystack before occurence of the needle.
29. namespace, import, and goto become reserved words.