Leggendo la documentazione sembra che "post_max_size" dev'essere più grande rispetto a "upload_max_filesize".

"upload_max_filesize int

The maximum size of an uploaded file.
post_max_size must be larger than this value.
When an int is used, the value is measured in bytes. Shorthand notation, as described in this FAQ, may also be used. "

Note:

PHP allows shortcuts for byte values, including K (kilo), M (mega) and G (giga). PHP will do the conversions automatically if you use any of these. Be careful not to exceed the 32 bit signed integer limit (if you're using 32bit versions) as it will cause your script to fail.

Per quanto riguarda "max_execution_time" penso si deve modifificare anche il Timeout del server apache/IIS che di default è 300 secondi, altrimenti le nuove regole imposte al PHP.INI non vengono rispettate (600 secondi).
Dunque per Apache devi modificare il file e riavviare il server in questo modo :

(su linux)
> sudo vi /etc/apache2/apache2.conf
> TimeOut 600
> sudo service apache2 restart

"max_execution_time

Your web server can have other timeout configurations that may also interrupt PHP execution. Apache has a Timeout directive and IIS has a CGI timeout function. Both default to 300 seconds. See your web server documentation for specific details."