how to develop custom module in magento

http://www.phpzag.com/create-custom-module-with-custom-database-table/
http://www.webspeaks.in/2010/08/create-your-first-adminbackend-module.html
http://www.magentocommerce.com/wiki/5_-_modules_and_development/0_-_module_development_in_magento/custom_module_with_custom_database_table

Check php version | php configuration

<?php phpinfo(); ?>