---- Pass by ref / pass by val: functions ----
NULL
string(11) "Ref changed"
NULL
NULL
NULL
string(11) "Ref changed"
string(11) "Ref changed"
NULL
string(12) "Ref1 changed"
string(12) "Ref2 changed"


 ---- Pass by ref / pass by val: static method calls ----
NULL
string(11) "Ref changed"
NULL
NULL
NULL
string(11) "Ref changed"
string(11) "Ref changed"
NULL
string(12) "Ref1 changed"
string(12) "Ref2 changed"


 ---- Pass by ref / pass by val: instance method calls ----
NULL
string(11) "Ref changed"
NULL
string(11) "Ref changed"
NULL
NULL
NULL
string(11) "Ref changed"
string(11) "Ref changed"
NULL
string(12) "Ref1 changed"
string(12) "Ref2 changed"