confirm behavior of exception and implications for objects

I just want to confirm my understanding of exceptions and how they impact their objects.

If I throw an exception, that halts the processing of a method, correct? So there's no point in doing

if ( some_check() ) {
    throw new Exception(...);
} else {
    ...
}

I should just do this

if ( some_ch开发者_如何学Pythoneck() ) {
    throw new Exception(...);
} 

rest_of_code();

Also, if I throw an exception in __construct, that destroys the object, right? So I should do all my argument validation exception-throwing right up front -- there's no point in building the object if it's gonna get blown up anyway in an input validation exception.

Yep you got it right :D You have a vote up from me :D

Allthough consider this, you might have two tests on one data :D

if( checkOne (a)){
   throw new Exception(...);
}
else (checkTwo(a)){
...

It's quite normal to throw an exception in a constructor, you are left with no other option. Also you did not mention objects that hold some sort of memory resource, make sure you are using a using statement or a try / catch / finally and release the memory with the exception.