Type-casting to boolean

Question

Can someone explain me why this:

var_dump((bool) 1==2); 

returns

bool(true) 

but

var_dump(1==2); 

returns

bool(false) 

Of course the second return is correct, but why in the first occasion php returns an unexpected value?

Answer 1

It's actually not as strange it seems. (bool) has higher precedence than ==, so this:

var_dump((bool) 1==2); 

is equivalent to this:

var_dump(  ((bool) 1)   == 2); 

or this:

var_dump(true == 2); 

Due to type juggling, the 2 also essentially gets cast to bool (since this is a "loose comparison"), so it's equivalent to this:

var_dump(true == true); 

or this:

var_dump(true); 

Answer 2

Because in the first example, the cast takes place before the comparison. So it's as if you wrote

((bool) 1)==2 

which is equivalent to

true == 2 

which is evaluated by converting 2 to true and comparing, ultimately producing true.

To see the expected result you need to add parens to make the order explicit:

var_dump((bool)(1==2)); 

See it in action.