Soluciónalo entrando en el fichero php.ini y poniendo un valor por ejemplo de 120 en esta variable.
max_execution_time
integer- This sets the maximum time in seconds a script is allowed to run before it is terminated by the parser. This helps prevent poorly written scripts from tying up the server. The default setting is 30. When running PHP from the command line the default setting is 0.
The maximum execution time is not affected by system calls, stream operations etc. Please see the set_time_limit() function for more details.
You can not change this setting with ini_set() when running in safe mode. The only workaround is to turn off safe mode or by changing the time limit in the php.ini.
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.