break ends execution of the current for, foreach, while, do-while or switch structure.
break accepts an optional numeric argument which tells it how many nested enclosing structures are to be broken out of. The default value is 1, only the immediate enclosing structure is broken out of.
7.0.0 break outside of a loop or switch control structure is now detected at compile-time instead of run-time as before, and triggers an E_COMPILE_ERROR.
5.4.0 break 0; is no longer valid. In previous versions it was interpreted the same as break 1;.
5.4.0 Removed the ability to pass in variables (e.g., $num = 2; break $num;) as the numerical argument.
It's not necessary to break out of any case of a switch statement in PHP, but if you want only one case to be executed, you have do break out of it (even out of the default case).
Note that the PHP documentation does not state the default part must be the last case statement.
If the numerical argument is higher than the number of things which can be broken out of, it seems to me like the execution of the entire program is stopped.
My program had 8 nested loops. Didn't bother counting them, but wrote: break 10. - Result: Code following the loops was not processed.