The manual says it enough.

auto_append_file string

Note: If the script is terminated with exit(), auto-append will not occur.

In interfaces you can force the return type

interface InterfaceTest {
    function GetSingleEntity(): Entity;
    function GetEntitySet() : Entity[];
}

GetEntitySet should return a array containing Entities. But this kind of syntax is not allowed.
You could just change it to only return an array, but the forcing of the class is the most powerful.
The best is to create a wrapper class for the entities, best would be to use an Iterator.

for ( $i=0; $i <= 5; $i++ ) {
    echo "for $i <br/>\n";
}

echo "done $i <br/>\n";

What will $i be, when the loop is done?

It will be 6 not 5.
Can be usefull if you need to skip the last item in a (numbered) array

During WordCamp Rotterdam I worked on a small bug in WP-CLI. A bug I found roughly six months ago.
The bug itself was a one line fix.
I was asked to create functional tests using behat which I didn’t even heard off.

So after checking the handbook and with help of a few others. It resulted in this pull request.
And now we wait.

Consider this dummy snippet:

if ( true === $skip || heavy_check() ){
    continue;
}

The $skip is checked first. It is very quick as it is just a simple variable check. and since this is an ‘or’ statement. As soon as $skip is true it won’t bother with the heavy_check.

Something I always suspected but today I tested this and confirmed it.