I'm attempting to appreciate this: If you will find errors within the database like FK issues, Missing tables/posts, or even when the database is dead -> Will this crash the applying? I've this site in php. How about application and network related errors? Can these cases be caught for and also have a deal with without customers visiting a non functionaning site or site lower message?
You will find a number of ways to identify errors and take care of them in PHP.
Exceptions, and check out-Catch claims.
Here's examples of both.
mysql_query( querystuff ) or die( mysql_error() );
Generally you should check each and every little bit of the application, from database connectivity to user input using php. That link assisted me a while ago http://www.nyphp.org/PHundamentals/7_PHP-Error-Handling It outlines try/catch error handling.