Returns the first member of an array, that is $array(1).
array:head( $array as array(*)item()*The function returns first member of $array, that is the value of $array(1).
The expression array:head([5, 6, 7, 8]) returns 5.
The expression array:head([["a", "b"], ["c", "d"]]) returns ["a", "b"].
The expression array:head([("a", "b"), ("c", "d")]) returns "a", "b".
A dynamic error occurs if $array is empty.
