You may also need to look at Apache's timeout setting, as you can change the max execution time value in php.ini and still get stopped by Apache's timeout value in the httpd.conf file.
You can find httpd.conf by running httpd -V in terminal (The command name depends on your system/apache version, it can be also apache -V) ~ If you don't have terminal access, you may need to contact your webhost. Example output:
bash-3.2# httpd -V
Server version: Apache/2.2.22 (Unix)
Server built: Aug 24 2012 17:16:58
Server's Module Magic Number: 20051115:30
Server loaded: APR 1.4.5, APR-Util 1.3.12
Compiled using: APR 1.4.5, APR-Util 1.3.12
Server MPM: Prefork
forked: yes (variable process count)
Server compiled with....
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D SERVER_CONFIG_FILE="/private/etc/apache2/httpd.conf" <-- HERE IT IS
httpd.conf could look like this:
Notice the line: