Execution time error

How can change execution time more than 30 seconds

you have two ways to do that :

1) Change the max_execution_time setting of your php.ini file
(see http://php.net/manual/en/info.configuration.php). Doing this way will affect all the scriptsrunning on your server
2) Call the set_time_limit() function from your script (see http://php.net/manual/en/function.set-time-limit.php). This will only affect the current script's max execution time.

In both cases, you will need to specify a maximum number of seconds. A value of zero means "no limit".

Note that you may not be able to change this setting if you are running in a shared host environment.