The example about static variables in the  manual page for "unset" is broken : the output is actually 1 2 3 (not 1 1 1) there is no reset.

function foo() {
    static $a;
    $a++;
       echo "$a\n";

    unset($a);
}

foo();foo();foo()

From the discussion of bugs 2015, 6810, and 13967 it seems it is clearly an error in the doc.

Ivan