If I have an “array” and can do array[0] to get first item, but when I filter this array and array[0] throws an error, that’s super weird. What is the meaning of [] or what is an array even? The language forces me to understand how it is implemented under the hood. That’s exactly what the author says: leaky abstraction.
That also often shoots you as when json_encoding it only becomes an array when ordered "correctly" (numeric 0-based keys without gaps), otherwise an object. So to be safe you generally need to array_values after filtering. If in your testdata you only remove elements from the end you don't catch that before production data hits.
To get the first element there also is reset().
I love PHP though.